1
H
Hydrogen
1.0079 amu
Hydrogen
Discoverer: Cavendish, Henry
Element Category: Non Metal
Hydrogenis a chemical element withatomic number1which means there are 1 protons and 1 electrons in the atomic structure. Thechemical symbolfor Hydrogen isH.
With a standard atomic weight of circa 1.008, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.
1.0079 amu
2
He
Helium
4.0026 amu
Helium
Discoverer: Ramsey, Sir William and Cleve, Per Teodor
Element Category: Noble gas
Helium is a chemical element with atomic number 2 which means there are 2 protons and 2 electrons in the atomic structure. The chemical symbol for Helium is He.
It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic table. Its boiling point is the lowest among all the elements.
4.0026 amu
3
Li
Lithium
6.941 amu
Lithium
Discoverer: Arfvedson, Johan August
Element Category: Alkali metal
Lithiumis a chemical element withatomic number3which means there are 3 protons and 3 electrons in the atomic structure. Thechemical symbolfor Lithium isLi.
It is a soft, silvery-white alkali metal. Under standard conditions, it is the lightest metal and the lightest solid element. Like all alkali metals, lithium is highly reactive and flammable, and is stored in mineral oil.
6.941 amu
4
Be
Beryllium
9.0122 amu
Beryllium
Discoverer: Vauquelin, Nicholas Louis
Element Category: Alkaline earth metal
Berylliumis a chemical element withatomic number4which means there are 4 protons and 4 electrons in the atomic structure. Thechemical symbolfor Beryllium isBe.
Beryllium is a hard, grayish metal naturally found in mineral rocks, coal, soil, and volcanic dust. The commercial use of beryllium requires the use of appropriate dust control equipment and industrial controls at all times because of the toxicity of inhaled beryllium-containing dusts that can cause a chronic life-threatening allergic disease in some people called berylliosis.
9.0122 amu
5
B
Boron
10.811 amu
Boron
Discoverer: Davy, Sir H. and Thénard, L.-J. and Gay-Lussac, L.-J.
Element Category: Metalloids
Boronis a chemical element withatomic number5which means there are 5 protons and 5 electrons in the atomic structure. Thechemical symbolfor Boron isB.
Significant concentrations of boron occur on the Earth in compounds known as the borate minerals. There are over 100 different borate minerals, but the most common are: borax, kernite, ulexite etc. Natural boron consists primarily of two stable isotopes, 11B (80.1%) and 10B (19.9%). In nuclear industry boron is commonly used as a neutron absorber due to the high neutron cross-section of isotope 10B.
10.811 amu
6
C
Carbon
12.0107 amu
Carbon
Discoverer: unknown
Element Category: Nonmetals
Carbonis a chemical element withatomic number6which means there are 6 protons and 6 electrons in the atomic structure. Thechemical symbolfor Carbon isC.
It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. Carbon is one of the few elements known since antiquity. Carbon is the 15th most abundant element in the Earth’s crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen.
12.0107 amu
7
N
Nitrogen
14.0067 amu
Nitrogen
Discoverer: Rutherford, Daniel
Element Category: Nonmetals
Nitrogenis a chemical element withatomic number7which means there are 7 protons and 7 electrons in the atomic structure. Thechemical symbolfor Nitrogen isN.
Nitrogen is a colourless, odourless unreactive gas that forms about 78% of the earth’s atmosphere. Liquid nitrogen (made by distilling liquid air) boils at 77.4 kelvins (−195.8°C) and is used as a coolant.
14.0067 amu
8
O
Oxygen
15.9994 amu
Oxygen
Discoverer: Priestley, Joseph and Scheele, Carl Wilhelm
Element Category: Nonmetals
Oxygenis a chemical element withatomic number8which means there are 8 protons and 8 electrons in the atomic structure. Thechemical symbolfor Oxygen isO.
Oxygen is a colourless, odourless reactive gas, the chemical element of atomic number 8 and the life-supporting component of the air. It is a member of the chalcogen group on the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium.
15.9994 amu
9
F
Fluorine
18.9984 amu
Fluorine
Discoverer: Moissan, Henri
Element Category: Nonmetals
Fluorineis a chemical element withatomic number9which means there are 9 protons and 9 electrons in the atomic structure. Thechemical symbolfor Fluorine isF.
Fluorine is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. As the most electronegative element, it is extremely reactive: almost all other elements, including some noble gases, form compounds with fluorine.
18.9984 amu
10
Ne
Neon
20.1797 amu
Neon
Discoverer: Ramsay, William and Travers, Morris
Element Category: Noble gas
Neonis a chemical element withatomic number10which means there are 10 protons and 10 electrons in the atomic structure. Thechemical symbolfor Neon isNe.
Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air.
20.1797 amu
11
Na
Sodium
22.9897 amu
Sodium
Discoverer: Davy, Sir Humphry
Element Category: Alkali metal
Sodiumis a chemical element withatomic number11which means there are 11 protons and 11 electrons in the atomic structure. Thechemical symbolfor Sodium isNa.
Sodium is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table, because it has a single electron in its outer shell that it readily donates, creating a positively charged atom—the Na+ cation.
22.9897 amu
12
Mg
Magnesium
24.305 amu
Magnesium
Discoverer: Black, Joseph
Element Category: Alkaline earth metal
Magnesiumis a chemical element withatomic number12which means there are 12 protons and 12 electrons in the atomic structure. Thechemical symbolfor Magnesium isMg.
Magnesium is a shiny gray solid which bears a close physical resemblance to the other five elements in the second column (group 2, or alkaline earth metals) of the periodic table: all group 2 elements have the same electron configuration in the outer electron shell and a similar crystal structure.
24.305 amu
13
Al
Aluminium
26.9815 amu
Aluminium
Discoverer: Oersted, Hans Christian
Element Category: Post-transition metals
Aluminumis a chemical element withatomic number13which means there are 13 protons and 13 electrons in the atomic structure. Thechemical symbolfor Aluminum isAl.
Aluminium is a silvery-white, soft, nonmagnetic, ductile metal in the boron group. By mass, aluminium makes up about 8% of the Earth’s crust; it is the third most abundant element after oxygen and silicon and the most abundant metal in the crust, though it is less common in the mantle below.
26.9815 amu
14
Si
Silicon
28.0855 amu
Silicon
Discoverer: Berzelius, Jöns Jacob
Element Category: Metalloids
Siliconis a chemical element withatomic number14which means there are 14 protons and 14 electrons in the atomic structure. Thechemical symbolfor Silicon isSi.
Silicon is a hard and brittle crystalline solid with a blue-grey metallic lustre, it is a tetravalent metalloid and semiconductor.
28.0855 amu
15
P
Phosphorus
30.9738 amu
Phosphorus
Discoverer: Brandt, Hennig
Element Category: Nonmetal
Phosphorusis a chemical element withatomic number15which means there are 15 protons and 15 electrons in the atomic structure. Thechemical symbolfor Phosphorus isP.
As an element, phosphorus exists in two major forms—white phosphorus and red phosphorus—but because it is highly reactive, phosphorus is never found as a free element on Earth. At 0.099%, phosphorus is the most abundant pnictogen in the Earth’s crust.
30.9738 amu
16
S
Sulfur
32.065 amu
Sulfur
Discoverer: unknown
Element Category: Nonmetal
Sulfuris a chemical element withatomic number16which means there are 16 protons and 16 electrons in the atomic structure. Thechemical symbolfor Sulfur isS.
Sulfur is abundant, multivalent, and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula S8. Elemental sulfur is a bright yellow crystalline solid at room temperature. Chemically, sulfur reacts with all elements except for gold, platinum, iridium, tellurium, and the noble gases.
32.065 amu
17
Cl
Chlorine
35.453 amu
Chlorine
Discoverer: Scheele, Carl Wilhelm
Element Category: Nonmetal
Chlorineis a chemical element withatomic number17which means there are 17 protons and 17 electrons in the atomic structure. Thechemical symbolfor Chlorine isCl.
Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity, behind only oxygen and fluorine.
35.453 amu
18
Ar
Argon
39.948 amu
Argon
Discoverer: Ramsay, Sir William and Strutt, John (Lord Rayleigh)
Element Category: Noble gas
Argonis a chemical element withatomic number18which means there are 18 protons and 18 electrons in the atomic structure. Thechemical symbolfor Argon isAr.
Argon is the third-most abundant gas in the Earth’s atmosphere, at 0.934% (9340 ppmv). Argon is mostly used as an inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive; for example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning.
39.948 amu
19
K
Potassium
39.0983 amu
Potassium
Discoverer: Davy, Sir Humphry
Element Category: Alkali metal
Potassiumis a chemical element withatomic number19which means there are 19 protons and 19 electrons in the atomic structure. Thechemical symbolfor Potassium isK.
Potassium was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals. All of the alkali metals have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge – a cation, which combines with anions to form salts. Naturally occurring potassium is composed of three isotopes, of which 40K is radioactive.
39.0983 amu
20
Ca
Calcium
40.078 amu
Calcium
Discoverer: Davy, Sir Humphry
Element Category: Alkaline earth metal
Calciumis a chemical element withatomic number20which means there are 20 protons and 20 electrons in the atomic structure. Thechemical symbolfor Calcium isCa.
Calcium is an alkaline earth metal, it is a reactive pale yellow metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth’s crust and the third most abundant metal, after iron and aluminium.
40.078 amu
21
Sc
Scandium
44.9559 amu
Scandium
Discoverer: Nilson, Lars Fredrik
Element Category: Transition metals
Scandiumis a chemical element withatomic number21which means there are 21 protons and 21 electrons in the atomic structure. Thechemical symbolfor Scandium isSc.
Scandium is a silvery-white metallic d-block element, it has historically been sometimes classified as a rare-earth element, together with yttrium and the lanthanides.
44.9559 amu
22
Ti
Titanium
47.867 amu
Titanium
Discoverer: Gregor, William
Element Category: Transition metals
Titaniumis a chemical element withatomic number22which means there are 22 protons and 22 electrons in the atomic structure. Thechemical symbolfor Titanium isTi. Titanium is a lustrous transition metal with a silver color, low density, and high strength. Titanium is resistant to corrosion in sea water, aqua regia, and chlorine. Titanium can be used in surface condensers. These condensers use tubes that are usually made of stainless steel, copper alloys, or titanium depending on several selection criteria (such as thermal conductivity or corrosion resistance). Titanium condenser tubes are usually the best technical choice, however titanium is very expensive material.
47.867 amu
23
V
Vanadium
50.9415 amu
Vanadium
Discoverer: Del Rio, Andrés Manuel (1801) and Sefström, Nils Gabriel (1830)
Element Category: Transition metals
Vanadiumis a chemical element withatomic number23which means there are 23 protons and 23 electrons in the atomic structure. Thechemical symbolfor Vanadium isV.
Vanadium is a hard, silvery grey, ductile, and malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer (passivation) stabilizes the free metal somewhat against further oxidation.
50.9415 amu
24
Cr
Chromium
51.9961 amu
Chromium
Discoverer: Vauquelin
Element Category: Transition metals
Chromiumis a chemical element withatomic number24which means there are 24 protons and 24 electrons in the atomic structure. Thechemical symbolfor Chromium isCr.
Chromium is a steely-grey, lustrous, hard and brittle metal4 which takes a high polish, resists tarnishing, and has a high melting point. A major development was the discovery that steel could be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel.
51.9961 amu
25
Mn
Manganese
54.9381 amu
Manganese
Discoverer: Gahn, Johan Gottlieb
Element Category: Transition metals
Manganeseis a chemical element withatomic number25which means there are 25 protons and 25 electrons in the atomic structure. Thechemical symbolfor Manganese isMn.
Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.
54.9381 amu
26
Fe
Iron
55.845 amu
Iron
Discoverer: unknown
Element Category: Transition metals
Ironis a chemical element withatomic number26which means there are 26 protons and 26 electrons in the atomic structure. Thechemical symbolfor Iron isFe.
Iron is a metal in the first transition series. It is by mass the most common element on Earth, forming much of Earth’s outer and inner core. It is the fourth most common element in the Earth’s crust. Its abundance in rocky planets like Earth is due to its abundant production by fusion in high-mass stars.
55.845 amu
27
Co
Cobalt
58.9332 amu
Cobalt
Discoverer: Brandt, Georg
Element Category: Transition metals
Cobaltis a chemical element withatomic number27which means there are 27 protons and 27 electrons in the atomic structure. Thechemical symbolfor Cobalt isCo.
Cobalt is found in the Earth’s crust only in chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal.
58.9332 amu
28
Ni
Nickel
58.6934 amu
Nickel
Discoverer: Cronstedt, Alex Fredrik
Element Category: Transition metals
Nickelis a chemical element withatomic number28which means there are 28 protons and 28 electrons in the atomic structure. Thechemical symbolfor Nickel isNi.
Nickel is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile.
58.6934 amu
29
Cu
Copper
63.546 amu
Copper
Discoverer: unknown
Element Category: Transition metals
Copperis a chemical element withatomic number29which means there are 29 protons and 29 electrons in the atomic structure. Thechemical symbolfor Copper isCu.
Copper is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a reddish-orange color. Copper is used as a conductor of heat and electricity, as a building material, and as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins.
63.546 amu
30
Zn
Zinc
65.409 amu
Zinc
Discoverer: unknown
Element Category: Transition metals
Zincis a chemical element withatomic number30which means there are 30 protons and 30 electrons in the atomic structure. Thechemical symbolfor Zinc isZn.
In some respects zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn2+ and Mg2+ ions are of similar size.
65.409 amu
31
Ga
Gallium
69.723 amu
Gallium
Discoverer: Lecoq de Boisbaudran, Paul-Émile
Element Category: Post-transition metals
Galliumis a chemical element withatomic number31which means there are 31 protons and 31 electrons in the atomic structure. Thechemical symbolfor Gallium isGa.
Gallium has similarities to the other metals of the group, aluminium, indium, and thallium. Gallium does not occur as a free element in nature, but as gallium(III) compounds in trace amounts in zinc ores and in bauxite.
69.723 amu
32
Ge
Germanium
72.64 amu
Germanium
Discoverer: Winkler, Clemens A.
Element Category: Metalloids
Germaniumis a chemical element withatomic number32which means there are 32 protons and 32 electrons in the atomic structure. Thechemical symbolfor Germanium isGe.
Germanium is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. Pure germanium is a semiconductor with an appearance similar to elemental silicon.
72.64 amu
33
As
Arsenic
74.9216 amu
Arsenic
Discoverer: unknown
Element Category: Metalloids
Arsenicis a chemical element withatomic number33which means there are 33 protons and 33 electrons in the atomic structure. Thechemical symbolfor Arsenic isAs.
Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid.
74.9216 amu
34
Se
Selenium
78.96 amu
Selenium
Discoverer: Berzelius, Jöns Jacob
Element Category: Nonmetal
Seleniumis a chemical element withatomic number34which means there are 34 protons and 34 electrons in the atomic structure. Thechemical symbolfor Selenium isSe.
Selenium is a nonmetal with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. It rarely occurs in its elemental state or as pure ore compounds in the Earth’s crust.
78.96 amu
35
Br
Bromine
79.904 amu
Bromine
Discoverer: Balard, Antoine-Jérôme
Element Category: Nonmetal
Bromineis a chemical element withatomic number35which means there are 35 protons and 35 electrons in the atomic structure. Thechemical symbolfor Bromine isBr.
Bromine is the third-lightest halogen, and is a fuming red-brown liquid at room temperature that evaporates readily to form a similarly coloured gas. Its properties are thus intermediate between those of chlorine and iodine.
79.904 amu
36
Kr
Krypton
83.798 amu
Krypton
Discoverer: Ramsay, Sir William and Travers, Morris
Element Category: Noble gas
Kryptonis a chemical element withatomic number36which means there are 36 protons and 36 electrons in the atomic structure. Thechemical symbolfor Krypton isKr.
Krypton is a member of group 18 (noble gases) elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere and is often used with other rare gases in fluorescent lamps.
83.798 amu
37
Rb
Rubidium
85.4678 amu
Rubidium
Discoverer: Bunsen, Robert Wilhelm and Kirchhoff, Gustav Robert
Element Category: Alkali metals
Rubidiumis a chemical element withatomic number37which means there are 37 protons and 37 electrons in the atomic structure. Thechemical symbolfor Rubidium isRb.
Rubidium is a soft, silvery-white metallic element of the alkali metal group, with an atomic mass of 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other alkali metals, including rapid oxidation in air.
85.4678 amu
38
Sr
Strontium
87.62 amu
Strontium
Discoverer: Crawford, Adair
Element Category: Alkaline earth metals
Strontiumis a chemical element withatomic number38which means there are 38 protons and 38 electrons in the atomic structure. Thechemical symbolfor Strontium isSr.
Strontium is an alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly reactive chemically.
87.62 amu
39
Y
Yttrium
88.9059 amu
Yttrium
Discoverer: Gadolin, Johan
Element Category: Transition metals
Yttriumis a chemical element withatomic number39which means there are 39 protons and 39 electrons in the atomic structure. Thechemical symbolfor Yttrium isY.
Yttrium is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a “rare-earth element”.
88.9059 amu
40
Zr
Zirconium
91.224 amu
Zirconium
Discoverer: Klaproth, Martin Heinrich
Element Category: Transition metals
Zirconiumis a chemical element withatomic number40which means there are 40 protons and 40 electrons in the atomic structure. Thechemical symbolfor Zirconium isZr. Zirconium is a lustrous, grey-white, strong transition metal that resembles hafnium and, to a lesser extent, titanium. Zirconium is mainly used as a refractory and opacifier, although small amounts are used as an alloying agent for its strong resistance to corrosion. Zirconium is widely used as a cladding for nuclear reactor fuels.
91.224 amu
41
Nb
Niobium
92.9064 amu
Niobium
Discoverer: Hatchet, Charles
Element Category: Transition metals
Niobiumis a chemical element withatomic number41which means there are 41 protons and 41 electrons in the atomic structure. Thechemical symbolfor Niobium isNb.
Niobium is a soft, grey, ductile transition metal, often found in the minerals pyrochlore (the main commercial source for niobium) and columbite.
92.9064 amu
42
Mo
Molybdenum
95.94 amu
Molybdenum
Discoverer: Scheele, Carl Welhelm
Element Category: Transition metals
Molybdenumis a chemical element withatomic number42which means there are 42 protons and 42 electrons in the atomic structure. Thechemical symbolfor Molybdenum isMo.
Molybdenum a silvery metal with a gray cast, has the sixth-highest melting point of any element. It readily forms hard, stable carbides in alloys, and for this reason most of world production of the element (about 80%) is used in steel alloys, including high-strength alloys and superalloys.
95.94 amu
43
Tc
Technetium
98 amu
Technetium
Discoverer: Perrier, Carlo and Segrè, Emilio
Element Category: Transition metals
Technetiumis a chemical element withatomic number43which means there are 43 protons and 43 electrons in the atomic structure. Thechemical symbolfor Technetium isTc.
Technetium is the lightest element whose isotopes are all radioactive; none are stable. Nearly all technetium is produced synthetically, and only minute amounts are found in the Earth’s crust. The chemical properties of this silvery gray, crystalline transition metal are intermediate between rhenium and manganese.
98 amu
44
Ru
Ruthenium
101.07 amu
Ruthenium
Discoverer: Klaus, Karl Karlovich
Element Category: Transition metals
Rutheniumis a chemical element withatomic number44which means there are 44 protons and 44 electrons in the atomic structure. Thechemical symbolfor Ruthenium isRu.
Ruthenium is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most other chemicals.
101.07 amu
45
Rh
Rhodium
102.9055 amu
Rhodium
Discoverer: Wollaston, William Hyde
Element Category: Transition metals
Rhodiumis a chemical element withatomic number45which means there are 45 protons and 45 electrons in the atomic structure. Thechemical symbolfor Rhodium isRh.
Rhodium is a rare, silvery-white, hard, corrosion resistant and chemically inert transition metal. It is a noble metal and a member of the platinum group.
102.9055 amu
46
Pd
Palladium
106.42 amu
Palladium
Discoverer: Wollaston, William Hyde
Element Category: Transition metals
Palladiumis a chemical element withatomic number46which means there are 46 protons and 46 electrons in the atomic structure. Thechemical symbolfor Palladium isPd.
Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). These have similar chemical properties, but palladium has the lowest melting point and is the least dense of them.
106.42 amu
47
Ag
Silver
107.8682 amu
Silver
Discoverer: unknown
Element Category: Transition metals
Silveris a chemical element withatomic number47which means there are 47 protons and 47 electrons in the atomic structure. Thechemical symbolfor Silver isAg.
Silver is a soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earth’s crust in the pure, free elemental form (“native silver”), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite.
107.8682 amu
48
Cd
Cadmium
112.411 amu
Cadmium
Discoverer: Stromeyer, Prof. Friedrich
Element Category: Transition metals
Cadmiumis a chemical element withatomic number48which means there are 48 protons and 48 electrons in the atomic structure. Thechemical symbolfor Cadmium isCd.
Cadmium is a soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. In nuclear industry cadmium is commonly used as a thermal neutron absorber due to very high neutron absorption cross-section of 113Cd. 113Cd has specific absorption cross-section.
112.411 amu
49
In
Indium
114.818 amu
Indium
Discoverer: Reich, Ferdinand and Richter, Hieronymus
Element Category: Post-transition metals
Indiumis a chemical element withatomic number49which means there are 49 protons and 49 electrons in the atomic structure. Thechemical symbolfor Indium isIn.
Indium is a post-transition metal that makes up 0.21 parts per million of the Earth’s crust. Very soft and malleable, indium has a melting point higher than sodium and gallium, but lower than lithium and tin. Chemically, indium is similar to gallium and thallium.
114.818 amu
50
Sn
Tin
118.71 amu
Tin
Discoverer: unknown
Element Category: Post-transition metals
Tinis a chemical element withatomic number50which means there are 50 protons and 50 electrons in the atomic structure. Thechemical symbolfor Tin isSn.
Tin is a post-transition metal in group 14 of the periodic table. It is obtained chiefly from the mineral cassiterite, which contains tin dioxide. The first alloy used on a large scale was bronze, made of tin and copper, from as early as 3000 BC.
118.71 amu
51
Sb
Antimony
121.76 amu
Antimony
Discoverer: unknown
Element Category: Metalloids
Antimonyis a chemical element withatomic number51which means there are 51 protons and 51 electrons in the atomic structure. Thechemical symbolfor Antimony isSb.
Antimony is a lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite. Antimony compounds have been known since ancient times and were powdered for use as medicine and cosmetics, often known by the Arabic name, kohl.
121.76 amu
52
Te
Tellurium
127.6 amu
Tellurium
Discoverer: Müller von Reichenstein, Franz Joseph
Element Category: Metalloids
Telluriumis a chemical element withatomic number52which means there are 52 protons and 52 electrons in the atomic structure. Thechemical symbolfor Tellurium isTe.
Tellurium is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur. It is occasionally found in native form as elemental crystals. Tellurium is far more common in the universe as a whole than on Earth. Its extreme rarity in the Earth’s crust, comparable to that of platinum.
127.6 amu
53
I
Iodine
126.9045 amu
Iodine
Discoverer: Courtois, Bernard
Element Category: Nonmetal
Iodineis a chemical element withatomic number53which means there are 53 protons and 53 electrons in the atomic structure. Thechemical symbolfor Iodine isI.
Iodine is the heaviest of the stable halogens, it exists as a lustrous, purple-black metallic solid at standard conditions that sublimes readily to form a violet gas. Iodine is the least abundant of the stable halogens, being the sixty-first most abundant element. It is even less abundant than the so-called rare earths. It is the heaviest essential mineral nutrient.
126.9045 amu
54
Xe
Xenon
131.293 amu
Xenon
Discoverer: Ramsay, William and Travers, Morris William
Element Category: Noble gas
Xenonis a chemical element withatomic number54which means there are 54 protons and 54 electrons in the atomic structure. Thechemical symbolfor Xenon isXe.
Xenon is a colorless, dense, odorless noble gas found in the Earth’s atmosphere in trace amounts. The name xenon for this gas comes from the Greek word ξένον [xenon], neuter singular form of ξένος [xenos], meaning ‘foreign(er)’, ‘strange(r)’, or ‘guest’. In nuclear industry, especially artificial xenon 135 has a tremendous impact on the operation of a nuclear reactor.
131.293 amu
55
Cs
Caesium
132.9055 amu
Caesium
Discoverer: Kirchhoff, Gustav and Bunsen, Robert
Element Category: Alkali metal
Caesiumis a chemical element withatomic number55which means there are 55 protons and 55 electrons in the atomic structure. Thechemical symbolfor Caesium isCs.
Caesium is a soft, silvery-gold alkali metal with a melting point of 28.5 °C, which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium has physical and chemical properties similar to those of rubidium and potassium.
132.9055 amu
56
Ba
Barium
137.327 amu
Barium
Discoverer: Davy, Sir Humphry
Element Category: Alkaline earth metals
Bariumis a chemical element withatomic number56which means there are 56 protons and 56 electrons in the atomic structure. Thechemical symbolfor Barium isBa.
Barium is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. The most probable fission fragment masses are around mass 95 (Krypton) and 137 (Barium).
137.327 amu
57-71
Lanthanoids
Lanthanoids
Discoverer: —
Element Category:
Lanthanoids comprise the 15 metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttrium, are often collectively known as the rare earth elements.
72
Hf
Hafnium
178.49 amu
Hafnium
Discoverer: Coster, Dirk and De Hevesy, George Charles
Element Category: Transition metals
Hafniumis a chemical element withatomic number72which means there are 72 protons and 72 electrons in the atomic structure. Thechemical symbolfor Hafnium isHf. Hafnium is a lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Hafnium’s large neutron capture cross-section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.
178.49 amu
73
Ta
Tantalum
180.9479 amu
Tantalum
Discoverer: Ekeberg, Anders Gustav
Element Category: Transition metals
Tantalumis a chemical element withatomic number73which means there are 73 protons and 73 electrons in the atomic structure. Thechemical symbolfor Tantalum isTa.
Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion-resistant.
180.9479 amu
74
W
Tungsten
183.84 amu
Tungsten
Discoverer: Elhuyar, Juan José and Elhuyar, Fausto
Element Category: Transition metals
Tungstenis a chemical element withatomic number74which means there are 74 protons and 74 electrons in the atomic structure. Thechemical symbolfor Tungsten isW.
Tungsten is a rare metal found naturally on Earth almost exclusively in chemical compounds. Tungsten is an intrinsically brittle and hard material, making it difficult to work.
183.84 amu
75
Re
Rhenium
186.207 amu
Rhenium
Discoverer: Noddack, Walter and Berg, Otto Carl and Tacke, Ida
Element Category: Transition metals
Rheniumis a chemical element withatomic number75which means there are 75 protons and 75 electrons in the atomic structure. Thechemical symbolfor Rhenium isRe.
Rhenium is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table.
186.207 amu
76
Os
Osmium
190.23 amu
Osmium
Discoverer: Tennant, Smithson
Element Category: Transition metals
Osmiumis a chemical element withatomic number76which means there are 76 protons and 76 electrons in the atomic structure. Thechemical symbolfor Osmium isOs. Osmium is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element, with a density of 22.59 g/cm3. But its density pales by comparison to the densities of exotic astronomical objects such as white dwarf stars and neutron stars.
190.23 amu
77
Ir
Iridium
192.217 amu
Iridium
Discoverer: Tennant, Smithson
Element Category: Transition metals
Iridiumis a chemical element withatomic number77which means there are 77 protons and 77 electrons in the atomic structure. Thechemical symbolfor Iridium isIr.
Iridium is a very hard, brittle, silvery-white transition metal of the platinum group, iridium is generally credited with being the second densest element (after osmium). It is also the most corrosion-resistant metal, even at temperatures as high as 2000 °C.
192.217 amu
78
Pt
Platinum
195.079 amu
Platinum
Discoverer: Ulloa, Antonio de
Element Category: Transition metals
Platinumis a chemical element withatomic number78which means there are 78 protons and 78 electrons in the atomic structure. Thechemical symbolfor Platinum isPt. Platinum is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Platinum is one of the least reactive metals. It has remarkable resistance to corrosion, even at high temperatures, and is therefore considered a noble metal. Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and jewelry.
195.079 amu
79
Au
Gold
196.9665 amu
Gold
Discoverer: unknown
Element Category: Transition metals
Goldis a chemical element withatomic number79which means there are 79 protons and 79 electrons in the atomic structure. Thechemical symbolfor Gold isAu.
Gold is a bright, slightly reddish yellow, dense, soft, malleable, and ductile metal. Gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements and is solid under standard conditions. Gold is thought to have been produced in supernova nucleosynthesis, from the collision of neutron stars.
196.9665 amu
80
Hg
Mercury
200.59 amu
Mercury
Discoverer: unknown
Element Category: Transition metals
Mercuryis a chemical element withatomic number80which means there are 80 protons and 80 electrons in the atomic structure. Thechemical symbolfor Mercury isHg.
Mercury is commonly known as quicksilver and was formerly named hydrargyrum. Mercury is a heavy, silvery d-block element, mercury is the only metallic element that is liquid at standard conditions for temperature and pressure.
200.59 amu
81
Tl
Thallium
204.3833 amu
Thallium
Discoverer: Crookes, William
Element Category: Post-transition metals
Thalliumis a chemical element withatomic number81which means there are 81 protons and 81 electrons in the atomic structure. Thechemical symbolfor Thallium isTl.
Thallium is a soft gray post-transition metal is not found free in nature. Commercially, thallium is produced as a byproduct from refining of heavy metal sulfide ores. Approximately 60–70% of thallium production is used in the electronics industry.
204.3833 amu
82
Pb
Lead
207.2 amu
Lead
Discoverer: unknown
Element Category: Post-transition metals
Leadis a chemical element withatomic number82which means there are 82 protons and 82 electrons in the atomic structure. Thechemical symbolfor Lead isPb.
Lead is a heavy metal that is denser than most common materials. Lead is soft and malleable, and has a relatively low melting point. Lead is widely used as a gamma shield. Major advantage of lead shield is in its compactness due to its higher density. Lead has the highest atomic number of any stable element and concludes three major decay chains of heavier elements.
207.2 amu
83
Bi
Bismuth
208.9804 amu
Bismuth
Discoverer: Geoffroy, Claude
Element Category: Post-transition metals
Bismuthis a chemical element withatomic number83which means there are 83 protons and 83 electrons in the atomic structure. Thechemical symbolfor Bismuth isBi.
Bismuth is a brittle metal with a silvery white color when freshly produced, but surface oxidation can give it a pink tinge. Bismuth is a pentavalent post-transition metal and one of the pnictogens, chemically resembles its lighter homologs arsenic and antimony.
208.9804 amu
84
Po
Polonium
209 amu
Polonium
Discoverer: Curie, Marie and Pierre
Element Category: Post-transition metals
Poloniumis a chemical element withatomic number84which means there are 84 protons and 84 electrons in the atomic structure. Thechemical symbolfor Polonium isPo.
Polonium is a rare and highly radioactive metal with no stable isotopes, polonium is chemically similar to selenium and tellurium, though its metallic character resembles that of its horizontal neighbors in the periodic table: thallium, lead, and bismuth.
209 amu
85
At
Astatine
210 amu
Astatine
Discoverer: Corson, Dale R. and Mackenzie, K. R.
Element Category: Metalloids
Astatineis a chemical element withatomic number85which means there are 85 protons and 85 electrons in the atomic structure. Thechemical symbolfor Astatine isAt.
Astatine is the rarest naturally occurring element on the Earth’s crust. It occurs on Earth as the decay product of various heavier elements. The bulk properties of astatine are not known with any certainty.
210 amu
86
Rn
Radon
222 amu
Radon
Discoverer: Dorn, Friedrich Ernst
Element Category: Noble gas
Radonis a chemical element withatomic number86which means there are 86 protons and 86 electrons in the atomic structure. Thechemical symbolfor Radon isRn.
Radon is a radioactive, colorless, odorless, tasteless noble gas. Radon occurs naturally as an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead.
222 amu
87
Fr
Francium
223 amu
Francium
Discoverer: Perey, Marguerite
Element Category: Alkali metal
Franciumis a chemical element withatomic number87which means there are 87 protons and 87 electrons in the atomic structure. Thechemical symbolfor Francium isFr.
Francium is an alkali metal, that has one valence electron. Francium is the second-least electronegative element, behind only caesium, and is the second rarest naturally occurring element (after astatine). Francium is a highly radioactive metal that decays into astatine, radium, and radon.
223 amu
88
Ra
Radium
226 amu
Radium
Discoverer: Curie, Marie and Pierre
Element Category: Alkaline earth metal
Radiumis a chemical element withatomic number88which means there are 88 protons and 88 electrons in the atomic structure. Thechemical symbolfor Radium isRa.
Pure radium is silvery-white alkaline earth metal. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226.
226 amu
89-103
Actinoids
Actinoids
Discoverer: —
Element Category:
The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.
104
Rf
Rutherfordium
261 amu
Rutherfordium
Discoverer: Scientists at Dubna, Russia (1964)/Albert Ghiorso et. al. (1969)
Element Category: Transition metal
Rutherfordiumis a chemical element withatomic number104which means there are 104 protons and 104 electrons in the atomic structure. Thechemical symbolfor Rutherfordium isRf.
261 amu
105
Db
Dubnium
262 amu
Dubnium
Discoverer: Scientists at Dubna, Russia (1967)/Lawrence Berkeley Laboratory (1970)
Element Category: Transition metal
Dubniumis a chemical element withatomic number105which means there are 105 protons and 105 electrons in the atomic structure. Thechemical symbolfor Dubnium isDb.
262 amu
106
Sg
Seaborgium
266 amu
Seaborgium
Discoverer: Albert Ghiorso et. al.
Element Category: Transition metal
Seaborgiumis a chemical element withatomic number106which means there are 106 protons and 106 electrons in the atomic structure. Thechemical symbolfor Seaborgium isSg.
266 amu
107
Bh
Bohrium
264 amu
Bohrium
Discoverer: Scientists at Dubna, Russia
Element Category: Transition metal
Bohriumis a chemical element withatomic number107which means there are 107 protons and 107 electrons in the atomic structure. Thechemical symbolfor Bohrium isBh.
264 amu
108
Hs
Hassium
277 amu
Hassium
Discoverer: Armbruster, Paula and Muenzenberg, Dr. Gottfried
Element Category: Transition metal
Hassiumis a chemical element withatomic number108which means there are 108 protons and 108 electrons in the atomic structure. Thechemical symbolfor Hassium isHs. It is a synthetic element (first synthesised at Hasse in Germany) and radioactive. The most stable known isotope,269Hs, has a half-life of approximately 9.7 seconds. It has an estimated density of 40.7 x 103kg/m3. The density of Hassium results from itshigh atomic weightand from the significant decrease inionic radiiof the elements in the lanthanide series, known aslanthanide and actinide contraction.
277 amu
109
Mt
Meitnerium
268 amu
Meitnerium
Discoverer: Armbruster, Paula and Muenzenberg, Dr. Gottfried
Element Category: unknown, probably a transition metal
Meitneriumis a chemical element withatomic number109which means there are 109 protons and 109 electrons in the atomic structure. Thechemical symbolfor Meitnerium isMt.
268 amu
110
Ds
Darmstadtium
281 amu
Darmstadtium
Discoverer: Armbruster, Paula and Muenzenberg, Dr. Gottfried
Element Category: unknown, probably a transition metal
Darmstadtiumis a chemical element withatomic number110which means there are 110 protons and 110 electrons in the atomic structure. Thechemical symbolfor Darmstadtium isDs.
281 amu
111
Rg
Roentgenium
272 amu
Roentgenium
Discoverer: David Anderson, Ruhani Rabin, Team Updraft
Element Category: unknown, probably a transition metal
Roentgeniumis a chemical element withatomic number111which means there are 111 protons and 111 electrons in the atomic structure. Thechemical symbolfor Roentgenium isRg.
272 amu
112
Cn
Copernicium
285 amu
Copernicium
Discoverer: Armbruster, Paula and Muenzenberg, Dr. Gottfried
Element Category: unknown, probably a transition metal
Coperniciumis a chemical element withatomic number112which means there are 112 protons and 112 electrons in the atomic structure. Thechemical symbolfor Copernicium isCn.
285 amu
113
Nh
Nihonium
286 amu
Nihonium
Discoverer: Y. T. Oganessian et. al.
Element Category: unknown, probably a transition metal
Nihoniumis a chemical element withatomic number113which means there are 113 protons and 113 electrons in the atomic structure. Thechemical symbolfor Nihonium isNh.
286 amu
114
Fl
Flerovium
289 amu
Flerovium
Discoverer: Scientists at Dubna, Russia
Element Category: unknown, probably a post-transition metal
Fleroviumis a chemical element withatomic number114which means there are 114 protons and 114 electrons in the atomic structure. Thechemical symbolfor Flerovium isFl.
289 amu
115
Mc
Moscovium
290 amu
Moscovium
Discoverer: Y. T. Oganessian et. al.
Element Category: unknown
Moscoviumis a chemical element withatomic number115which means there are 115 protons and 115 electrons in the atomic structure. Thechemical symbolfor Moscovium isMc.
290 amu
116
Lv
Livermorium
292 amu
Livermorium
Discoverer: Scientists at Dubna, Russia
Element Category: unknown
Livermoriumis a chemical element withatomic number116which means there are 116 protons and 116 electrons in the atomic structure. Thechemical symbolfor Livermorium isLv.
292 amu
117
Ts
Tennessine
294 amu
Tennessine
Discoverer: —
Element Category: unknown
Tennessineis a chemical element withatomic number117which means there are 117 protons and 117 electrons in the atomic structure. Thechemical symbolfor Tennessine isTs.
294 amu
118
Og
Oganesson
294 amu
Oganesson
Discoverer: Y. T. Oganessian et. al.
Element Category: unknown
Oganessonis a chemical element withatomic number118which means there are 118 protons and 118 electrons in the atomic structure. Thechemical symbolfor Oganesson isOg.
294 amu
57
La
Lanthanum
138.9055 amu
Lanthanum
Discoverer: Mosander, Carl Gustav
Element Category: Lanthanoids
Lanthanumis a chemical element withatomic number57which means there are 57 protons and 57 electrons in the atomic structure. Thechemical symbolfor Lanthanum isLa.
Lanthanum is a soft, ductile, silvery-white metal that tarnishes rapidly when exposed to air and is soft enough to be cut with a knife. It is the eponym of the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table, of which lanthanum is the first and the prototype. It is also sometimes considered the first element of the 6th-period transition metals and is traditionally counted among the rare earth elements.
138.9055 amu
58
Ce
Cerium
140.116 amu
Cerium
Discoverer: Hisinger, Wilhelm and Berzelius, Jöns Jacob/Klaproth, Martin Heinrich
Element Category: Lanthanoids
Ceriumis a chemical element withatomic number58which means there are 58 protons and 58 electrons in the atomic structure. Thechemical symbolfor Cerium isCe.
Cerium is a soft, ductile and silvery-white metal that tarnishes when exposed to air, and it is soft enough to be cut with a knife. Cerium is the second element in the lanthanide series. Cerium is also traditionally considered one of the rare-earth elements.
140.116 amu
59
Pr
Praseodymium
140.9077 amu
Praseodymium
Discoverer: Von Welsbach, Baron Auer
Element Category: Lanthanoids
Praseodymiumis a chemical element withatomic number59which means there are 59 protons and 59 electrons in the atomic structure. Thechemical symbolfor Praseodymium isPr.
Praseodymium is a soft, silvery, malleable and ductile metal, valued for its magnetic, electrical, chemical, and optical properties. Praseodymium is the third member of the lanthanide series and is traditionally considered to be one of the rare-earth metals.
140.9077 amu
60
Nd
Neodymium
144.24 amu
Neodymium
Discoverer: Von Welsbach, Baron Auer
Element Category: Lanthanoids
Neodymiumis a chemical element withatomic number60which means there are 60 protons and 60 electrons in the atomic structure. Thechemical symbolfor Neodymium isNd.
Neodymium is a soft silvery metal that tarnishes in air. Neodymium is not found naturally in metallic form or unmixed with other lanthanides, and it is usually refined for general use. Although neodymium is classed as a rare earth, it is a fairly common element.
144.24 amu
61
Pm
Promethium
145 amu
Promethium
Discoverer: Marinsky, Jacob A. and Coryell, Charles D. and Glendenin, Lawerence. E.
Element Category: Lanthanoids
Promethiumis a chemical element withatomic number61which means there are 61 protons and 61 electrons in the atomic structure. Thechemical symbolfor Promethium isPm.
Promethium is one of only two such elements that are followed in the periodic table by elements with stable forms. All of its isotopes are radioactive. In nuclear reactors, promethium equilibrium exists in power operation. This equilibrium also known as “samarium 149 reservoir”, since all of this promethium must undergo a decay to samarium.
145 amu
62
Sm
Samarium
150.36 amu
Samarium
Discoverer: Lecoq de Boisbaudran, Paul-Émile
Element Category: Lanthanoids
Samariumis a chemical element withatomic number62which means there are 62 protons and 62 electrons in the atomic structure. Thechemical symbolfor Samarium isSm. Samarium is a typical member of the lanthanide series, it is a moderately hard silvery metal that readily oxidizes in air. The name samarium is after the mineral samarskite from which it was isolated. Although classified as a rare earth element, samarium is the 40th most abundant element in the Earth’s crust and is more common than such metals as tin. In nuclear industry, especially natural and artificial samarium 149 has an important impact on the operation of a nuclear reactor.
150.36 amu
63
Eu
Europium
151.964 amu
Europium
Discoverer: Demarçay, Eugène-Antole
Element Category: Lanthanoids
Europiumis a chemical element withatomic number63which means there are 63 protons and 63 electrons in the atomic structure. Thechemical symbolfor Europium isEu.
Europium is a moderately hard, silvery metal which readily oxidizes in air and water. Being a typical member of the lanthanide series, europium usually assumes the oxidation state +3. Europium is one of the least abundant elements in the universe. Only about 5×10−8% of all matter in the universe is europium.
151.964 amu
64
Gd
Gadolinium
157.25 amu
Gadolinium
Discoverer: De Marignac, Charles Galissard
Element Category: Lanthanoids
Gadoliniumis a chemical element withatomic number64which means there are 64 protons and 64 electrons in the atomic structure. Thechemical symbolfor Gadolinium isGd.
Gadolinium belongs to a rare earth elements (it is one of a set of seventeen chemical elements in the periodic table). In nuclear industry gadolinium is commonly used as a neutron absorber due to very high neutron absorbtion cross-section of two isotopes 155Gd and 157Gd. In fact their absorption cross-sections are the highest among all stable isotopes.
157.25 amu
65
Tb
Terbium
158.9253 amu
Terbium
Discoverer: Mosander, Carl Gustav
Element Category: Lanthanoids
Terbiumis a chemical element withatomic number65which means there are 65 protons and 65 electrons in the atomic structure. Thechemical symbolfor Terbium isTb.
Terbium is a silvery-white, rare earth metal that is malleable, ductile, and soft enough to be cut with a knife. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas.
158.9253 amu
66
Dy
Dysprosium
162.5 amu
Dysprosium
Discoverer: Lecoq de Boisbaudran, Paul-Émile
Element Category: Lanthanoids
Dysprosiumis a chemical element withatomic number66which means there are 66 protons and 66 electrons in the atomic structure. Thechemical symbolfor Dysprosium isDy.
is a rare earth element with a metallic silver luster. Dysprosium is used for its high thermal neutron absorption cross-section in making control rods in nuclear reactors, for its high magnetic susceptibility in data storage applications.
162.5 amu
67
Ho
Holmium
164.9303 amu
Holmium
Discoverer: Cleve, Per Theodor
Element Category: Lanthanoids
Holmiumis a chemical element withatomic number67which means there are 67 protons and 67 electrons in the atomic structure. Thechemical symbolfor Holmium isHo.
Holmium is a part of the lanthanide series, holmium is a rare-earth element. Holmium is a relatively soft and malleable silvery-white metal.
164.9303 amu
68
Er
Erbium
167.259 amu
Erbium
Discoverer: Mosander, Carl Gustav
Element Category: Lanthanoids
Erbiumis a chemical element withatomic number68which means there are 68 protons and 68 electrons in the atomic structure. Thechemical symbolfor Erbium isEr.
Erbium is a silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements. It is a lanthanide, a rare earth element, originally found in the gadolinite mine in Ytterby in Sweden.
167.259 amu
69
Th
Thulium
168.9342 amu
Thulium
Discoverer: Cleve, Per Teodor
Element Category: Lanthanoids
Thuliumis a chemical element withatomic number69which means there are 69 protons and 69 electrons in the atomic structure. Thechemical symbolfor Thulium isTm.
Thulium is an easily workable metal with a bright silvery-gray luster. It is fairly soft and slowly tarnishes in air. Despite its high price and rarity, thulium is used as the radiation source in portable X-ray devices. Thulium is the thirteenth and third-last element in the lanthanide series.
168.9342 amu
70
Yb
Ytterbium
173.04 amu
Ytterbium
Discoverer: De Marignac, Jean Charles Galissard
Element Category: Lanthanoids
Ytterbiumis a chemical element withatomic number70which means there are 70 protons and 70 electrons in the atomic structure. Thechemical symbolfor Ytterbium isYb.
Because of its closed-shell electron configuration, its density and melting and boiling points differ significantly from those of most other lanthanides.
173.04 amu
71
Lu
Lutetium
174.967 amu
Lutetium
Discoverer: Urbain, Georges
Element Category: Lanthanoids
Lutetiumis a chemical element withatomic number71which means there are 71 protons and 71 electrons in the atomic structure. Thechemical symbolfor Lutetium isLu.
Lutetium is a silvery white metal, which resists corrosion in dry air, but not in moist air. Lutetium is the last element in the lanthanide series, and it is traditionally counted among the rare earths.
174.967 amu
89
Ac
Actinium
227 amu
Actinium
Discoverer: Debierne, André
Element Category: Actinoids
Actiniumis a chemical element withatomic number89which means there are 89 protons and 89 electrons in the atomic structure. Thechemical symbolfor Actinium isAc.
Actinium is a soft, silvery-white radioactive metal. Actinium gave the name to the actinide series, a group of 15 similar elements between actinium and lawrencium in the periodic table.
227 amu
90
Th
Thorium
232.0381 amu
Thorium
Discoverer: Berzelius, Jöns Jacob
Element Category: Actinoids
Thoriumis a chemical element withatomic number90which means there are 90 protons and 90 electrons in the atomic structure. Thechemical symbolfor Thorium isTh.
Thorium metal is silvery and tarnishes black when exposed to air, forming the dioxide. Thorium is moderately hard, malleable, and has a high melting point. Thorium is a naturally-occurring element and it is estimated to be about three times more abundant than uranium. Thorium is commonly found in monazite sands (rare earth metals containing phosphate mineral).
232.0381 amu
91
Pa
Protactinium
231.0359 amu
Protactinium
Discoverer: Göhring, Otto and Fajans, Kasimir
Element Category: Actinoids
Protactiniumis a chemical element withatomic number91which means there are 91 protons and 91 electrons in the atomic structure. Thechemical symbolfor Protactinium isPa.
Protactinium is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids.
231.0359 amu
92
U
Uranium
238.0289 amu
Uranium
Discoverer: Klaproth, Martin Heinrich
Element Category: Actinoids
Uraniumis a chemical element withatomic number92which means there are 92 protons and 92 electrons in the atomic structure. Thechemical symbolfor Uranium isU.
Uranium is a silvery-white metal in the actinide series of the periodic table. Uranium is weakly radioactive because all isotopes of uranium are unstable, with half-lives varying between 159,200 years and 4.5 billion years. Uranium has the highest atomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead, and slightly lower than that of gold or tungsten.
238.0289 amu
93
Np
Neptunium
237 amu
Neptunium
Discoverer: McMillan, Edwin M. and Abelson, Philip H.
Element Category: Actinoids
Neptuniumis a chemical element withatomic number93which means there are 93 protons and 93 electrons in the atomic structure. Thechemical symbolfor Neptunium isNp.
Neptunium metal is silvery and tarnishes when exposed to air. Neptunium is the first transuranic element.
237 amu
94
Pu
Plutonium
244 amu
Plutonium
Discoverer: Glenn T. Seaborg, Joseph W. Kennedy, Edward M. McMillan, Arthur C. Wohl
Element Category: Actinoids
Plutoniumis a chemical element withatomic number94which means there are 94 protons and 94 electrons in the atomic structure. Thechemical symbolfor Plutonium isPu.
Plutonium is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized.
244 amu
95
Am
Americium
243 amu
Americium
Discoverer: Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, Albert Ghiorso
Element Category: Actinoids
Americiumis a chemical element withatomic number95which means there are 95 protons and 95 electrons in the atomic structure. Thechemical symbolfor Americium isAm.
Americium is a transuranic member of the actinide series, in the periodic table located under the lanthanide element europium, and thus by analogy was named after the Americas.
243 amu
96
Cm
Curium
247 amu
Curium
Discoverer: Glenn T. Seaborg, Ralph A. James, Albert Ghiorso
Element Category: Actinoids
Curiumis a chemical element withatomic number96which means there are 96 protons and 96 electrons in the atomic structure. Thechemical symbolfor Curium isCm.
Curium is a hard, dense, silvery metal with a relatively high melting point and boiling point for an actinide.
247 amu
97
Bk
Berkelium
247 amu
Berkelium
Discoverer: Stanley G. Thompson, Glenn T. Seaborg, Kenneth Street, Jr., Albert Ghiorso
Element Category: Actinoids
Berkeliumis a chemical element withatomic number97which means there are 97 protons and 97 electrons in the atomic structure. Thechemical symbolfor Berkelium isBk.
Berkelium is a member of the actinide and transuranium element series.
247 amu
98
Cf
Californium
251 amu
Californium
Discoverer: Stanley G. Thompson, Glenn T. Seaborg, Kenneth Street, Jr., Albert Ghiorso
Element Category: Actinoids
Californiumis a chemical element withatomic number98which means there are 98 protons and 98 electrons in the atomic structure. Thechemical symbolfor Californium isCf.
Californium is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye (after einsteinium). The most commonly used spontaneous fission neutron source is the radioactive isotope californium-252.
251 amu
99
Es
Einsteinium
252 amu
Einsteinium
Discoverer: Albert Ghiorso et. al.
Element Category: Actinoids
Einsteiniumis a chemical element withatomic number99which means there are 99 protons and 99 electrons in the atomic structure. Thechemical symbolfor Einsteinium isEs.
Einsteinium is the seventh transuranic element, and an actinide.
252 amu
100
Fm
Fermium
257 amu
Fermium
Discoverer: Albert Ghiorso et. al.
Element Category: Actinoids
Fermiumis a chemical element withatomic number100which means there are 100 protons and 100 electrons in the atomic structure. Thechemical symbolfor Fermium isFm.
Fermium is a member of the actinide series. It is the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities.
257 amu
101
Md
Mendelevium
258 amu
Mendelevium
Discoverer: Stanley G. Thompson, Glenn T. Seaborg, Bernard G. Harvey, Gregory R. Choppin, Albert Ghiorso
Element Category: Actinoids
Mendeleviumis a chemical element withatomic number101which means there are 101 protons and 101 electrons in the atomic structure. Thechemical symbolfor Mendelevium isMd.
Mendelevium is a metallic radioactive transuranic element in the actinide series, it is the first element that currently cannot be produced in macroscopic quantities.
258 amu
102
No
Nobelium
259 amu
Nobelium
Discoverer: Albert Ghiorso, Glenn T. Seaborg, Torbørn Sikkeland, John R. Walton
Element Category: Actinoids
Nobeliumis a chemical element withatomic number102which means there are 102 protons and 102 electrons in the atomic structure. Thechemical symbolfor Nobelium isNo.
Nobelium is the tenth transuranic element and is the penultimate member of the actinide series. Like all elements with atomic number over 100, nobelium can only be produced in particle accelerators by bombarding lighter elements with charged particles.
259 amu
103
Lr
Lawrencium
262 amu
Lawrencium
Discoverer: Albert Ghiorso, Torbjørn Sikkeland, Almon E. Larsh, Robert M. Latimer
Element Category: Actinoids
Lawrenciumis a chemical element withatomic number103which means there are 103 protons and 103 electrons in the atomic structure. Thechemical symbolfor Lawrencium isLr.
Lawrencium is the final member of the actinide series. Like all elements with atomic number over 100, lawrencium can only be produced in particle accelerators by bombarding lighter elements with charged particles.
262 amu
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Atomic Mass of Nitrogen
Atomic mass ofNitrogenis14.0067 u.
The atomic mass is the mass of an atom. The atomic mass or relative isotopic mass refers to the mass of a single particle, and therefore is tied to a certain specific isotope of an element. The atomic mass is carried by the atomic nucleus, which occupies only about 10-12of the total volume of the atom or less, but it contains all the positive charge and at least 99.95% of the total mass of the atom. Note that, eachelementmay contain moreisotopes, therefore this resulting atomic mass is calculated from naturally-occuring isotopes and their abundance.
The size and mass of atoms are so small that the use of normal measuring units, while possible, is often inconvenient. Units of measure have been defined for mass and energy on the atomic scale to make measurements more convenient to express. The unit of measure for mass is theatomic mass unit (amu). One atomic mass unit is equal to 1.66 x 10-24grams. One unified atomic mass unit isapproximatelythe mass of one nucleon (either a single proton or neutron) and is numerically equivalent to 1 g/mol.
For12C the atomic mass is exactly 12u, since the atomic mass unit is defined from it. For other isotopes, the isotopic mass usually differs and is usually within 0.1 u of the mass number. For example,63Cu(29 protons and 34 neutrons) has a mass number of 63 and an isotopic mass in itsnuclear ground state is 62.91367 u.
There are two reasons for the difference between mass number and isotopic mass, known as themass defect:
- Theneutronisslightlyheavierthan theproton. This increases the mass of nuclei with more neutrons than protons relative to the atomic mass unit scale based on12C with equal numbers of protons and neutrons.
- Thenuclear binding energyvaries between nuclei. A nucleus with greater binding energy has a lower total energy, and therefore alower massaccording toEinstein’s mass-energy equivalencerelationE=mc2. For63Cuthe atomic mass is less than 63 so this must be the dominant factor.
Note that, it was found therest mass of an atomic nucleusis measurably smaller thanthe sum of the rest masses of its constituentprotons,neutronsand electrons. Mass was no longer considered unchangeable in the closed system. The difference is a measure of thenuclear binding energywhich holds the nucleus together. According to the Einstein relationship (E=mc2), this binding energy is proportional to thismass differenceand it is known as themass defect.
See also:Atomic Mass Number – Does it conserve in a nuclear reaction?
Mass Number of Nitrogen
Mass numbers of typical isotopes ofNitrogenare14; 15.
The total number ofneutronsin the nucleus of an atom is called theneutronnumberof the atom and is given thesymbol N. Neutronnumber plusatomic numberequals atomic mass number:N+Z=A. The difference between the neutron number and the atomic number is known as theneutron excess: D = N – Z = A – 2Z.
Neutron number is rarely written explicitly in nuclide symbol notation, but appears as a subscript to the right of the element symbol. Nuclides that have the same neutron number but a different proton number are called isotones. The various species of atoms whose nuclei contain particular numbers of protons and neutrons are callednuclides. Each nuclide is denoted by chemical symbol of the element (this specifies Z) with tha atomic mass number as supescript. Therefore, we cannot determine the neutron number of uranium, for example. We can determine the neutron number of certain isotope. For example, the neutron number of uranium-238 is 238-92=146.
Densityof Nitrogen
Density ofNitrogenis1.251g/cm3.
Typical densities of various substances are at atmospheric pressure.
Densityis defined as themass per unit volume. It is anintensive property, which is mathematically defined as mass divided by volume:
ρ = m/V
In words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit iskilograms per cubic meter(kg/m3). The Standard English unit ispounds mass per cubic foot(lbm/ft3).
Density – Atomic Mass and Atomic Number Density
Since the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance, it is obvious, the density of a substance strongly depends on its atomic mass and also onthe atomic number density(N; atoms/cm3),
- Atomic Weight. The atomic mass is carried by the atomic nucleus, which occupies only about 10-12of the total volume of the atom or less, but it contains all the positive charge and at least 99.95% of the total mass of the atom. Therefore it is determined by the mass number (number of protons and neutrons).
- Atomic Number Density. Theatomic number density(N; atoms/cm3), which is associated with atomic radii, is the number of atoms of a given type per unit volume (V; cm3) of the material. The atomic number density (N; atoms/cm3) of a pure material havingatomic or molecular weight(M; grams/mol) and thematerial density(⍴; gram/cm3) is easily computed from the following equation using Avogadro’s number (NA= 6.022×1023atoms or molecules per mole):
Sincenucleons(protonsandneutrons) make up most of the mass of ordinary atoms, the density of normal matter tends to be limited by how closely we can pack these nucleons and depends on the internal atomic structure of a substance. Thedensest materialfound on earth is themetal osmium, but its density pales by comparison to the densities of exotic astronomical objects such as whitedwarf starsandneutron stars.
If we include man made elements, the densest so far isHassium.Hassiumis a chemical element with symbolHsand atomic number 108. It is a synthetic element (first synthesised at Hasse in Germany) and radioactive. The most stable known isotope,269Hs, has a half-life of approximately 9.7 seconds. It has an estimated density of40.7 x 103kg/m3. The density of Hassium results from itshigh atomic weightand from the significant decrease inionic radiiof the elements in the lanthanide series, known aslanthanide and actinide contraction.
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