Atomic Number

The atomic number (Z) of an element is the number of protons each atom of that element has in its nucleus; e.g., Z = 17 for chlorine (17Cl).

The atomic number was originally defined as an index describing the position of an element in the periodic table and it was not until 1913 that it was known that it was a unit of measurement.

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Actinium 89 Clip Aluminium 13 Clip Americium 95 Clip
Antimony 51 Clip Argon 18 Clip Arsenic 33 Clip
Astatine 85 Clip Barium 56 Clip Berkelium 97 Clip
Beryllium 4 Clip Bismuth 83 Clip Boron 5 Clip
Bromine 35 Clip Cadmium 48 Clip Caesium 55 Clip
Calcium 20 Clip Californium 98 Clip Carbon 6 Clip
Cerium 58 Clip Chlorine 17 Clip Chromium 24 Clip
Cobalt 27 Clip Copernicium 112 Clip Copper 29 Clip
Curium 96 Clip Dysprosium 66 Clip Einsteinium 99 Clip
Erbium 68 Clip Europium 63 Clip Fermium 100 Clip
Fluorine 9 Clip Francium 87 Clip Gadolinium 64 Clip
Gallium 31 Clip Germanium 32 Clip Gold 79 Clip
Hafnium 72 Clip Helium 2 Clip Holmium 67 Clip
Hydrogen 1 Clip Indium 49 Clip Iodine 53 Clip
Iridium 77 Clip Iron 26 Clip Krypton 36 Clip
Lanthanum 57 Clip Lawrencium 103 Clip Lead 82 Clip
Lithium 3 Clip Lutetium 71 Clip Magnesium 12 Clip
Manganese 25 Clip Mendelevium 101 Clip Mercury Hg 80 Clip
Molybdenum 42 Clip Neodymium 60 Clip Neon 10 Clip
Neptunium 93 Clip Nickel 28 Clip Niobium 41 Clip
Nitrogen 7 Clip Nobelium 102 Clip Osmium 76 Clip
Oxygen 8 Clip Palladium 46 Clip Phosphorus 15 Clip
Platinum 78 Clip Plutonium 94 Clip Polonium 84 Clip
Potassium 19 Clip Praseodymium 59 Clip Promethium 61 Clip
Protactinium 91 Clip Radium 88 Clip Radon 86 Clip
Rhenium 75 Clip Rhodium 45 Clip Rubidium 37 Clip
Ruthenium 44 Clip Samarium 62 Clip Scandium 21 Clip
Selenium 34 Clip Silicon 14 Clip Silver 47 Clip
Sodium 11 Clip Strontium 38 Clip Sulphur 16 Clip
Tantalum 73 Clip Technetium 43 Clip Tellurium 52 Clip
Terbium 65 Clip Thallium 81 Clip Thorium 90 Clip
Thulium 69 Clip Tin 50 Clip Titanium 22 Clip
Tungsten 74 Clip Unnilhexium 106 Clip Unnilpentium 105 Clip
Unnilquadium 104 Clip Unnilseptium 107 Clip Uranium 92 Clip
Vanadium 23 Clip Xenon 54 Clip Ytterbium 70 Clip
Yttrium 39 Clip Zinc 30 Clip Zirconium 40 Clip
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See also: Atomic weight, Effective Nuclear Charge, Mass Number, Nuclide Symbol, Periodic Table.

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Subjects: Chemistry Nuclear and Particle Physics