Formulas and Composition

Submitted by ChemPRIME Staff on Wed, 12/08/2010 - 23:45

Text below taken from Table of Atomic Weights

Name Symbol Atomic Number Atomic Weight Name Symbol Atomic Number Atomic Weight
Actinium2 Ac 89 (227) Molybdenum Mo 42 95.96(2)
Aluminum Al 13 26.981 5386(8) Neodymium Nd 60 144.242(3)
Americium2 Am 95 (243) Neon Ne 10 20.1797(6)
Antimony Sb 51 121.760(1) Neptunium2 Np 93 (237)
Argon Ar 18 39.948(1) Nickel Ni 28 58.6934(4)
Arsenic As 33 74.92160(2) Niobium Nb 41 92.90638(2)
Astatine2 At 85 (210) Nitrogen N 7 14.0067(2)
Barium Ba 56 137.327(7) Nobelium2 No 102 (259)
Berkelium2 Bk 97 (247) Osmium Os 76 190.23(3)


Beryllium Be 4 9.012182(3) Oxygen O 8 15.9994(3)
Bismuth Bi 83 208.98040(1) Palladium Pd 46 106.42(1)
Bohrium2 Bh 107 (272) Phosphorus P 15 30.973762(2)
Boron B 5 10.811(7) Platinum Pt 78 195.084(9)
Bromine Br 35 79.904(1) Plutonium2 Pu 94 (244)
Cadmium Cd 48 112.411(8) Polonium2 Po 84 (209)
Calcium Ca 20 40.078(4) Potassium K 19 39.0983(1)
Californium2 Cf 98 (251) Praseodymium Pr 59 140.90765(2)
Carbon C 6 12.0107(8) Promethium2 Pm 61 (145)
Cerium Ce 58 140.116(1) Protactinium2 Pa 91 231.03588(2)
Cesium Cs 55 132.9054519(2) Radium2 Ra 88 (226)
Chlorine Cl 17 35.453(2) Radon2 Rn 86 (222)
Chromium Cr 24 51.9961(6) Rhenium Re 75 186.207(1)
Cobalt Co 27 58.933195(5) Rhodium Rh 45 102.90550(2)
Copper Cu 29 63.546(3) Roentgenium2 Rg 111 (280)
Curium2 Cm 96 (247) Rubidium Rb 37 85.4678(3)
Darmstadtium2 Ds 110 (281) Ruthenium Ru 44 101.07(2)
Dubnium2 Db 105 (268) Rutherfordium2 Rf 104 (267)
Dysprosium Dy 66 162.500(1) Samarium Sm 62 150.36(2)
Einsteinium2 Es 99 (252) Scandium Sc 21 44.955912(6)
Erbium Er 68 167.259(3) Seaborgium2 Sg 106 (271)
Europium Eu 63 151.964(1) Selenium Se 34 78.96(3)
Fermium2 Fm 100 (257) Silicon Si 14 28.0855(3)
Fluorine F 9 18.9984032(5) Silver Ag 47 107.8682(2)
Francium2 Fr 87 (223) Sodium Na 11 22.98976928(2)
Gadolinium Gd 64 157.25(3) Strontium Sr 38 87.62(1)
Gallium Ga 31 69.723(1) Sulfur S 16 32.065(5)
Germanium Ge 32 72.64(1) Tantalum Ta 73 180.94788(2)
Gold Au 79 196.966569(4) Technetium2 Tc 43 (98)
Hafnium Hf 72 178.49(2) Tellurium Te 52 127.60(3)
Hassium2 Hs 108 (277) Terbium Tb 65 158.92535(2)
Helium He 2 4.002602(2) Thallium Tl 81 204.3833(2)
Holmium Ho 67 164.93032(2) Thorium2 Th 90 232.03806(2)
Hydrogen H 1 1.00794(7) Thulium Tm 69 168.93421(2)
Indium In 49 114.818(3) Tin Sn 50 118.710(7)


Iodine I 53 126.90447(3) Titanium Ti 22 47.867(1)
Iridium Ir 49 192.217(3) Tungsten W 74 183.84(1)
Iron Fe 26 55.845(2) Uranium2 U 92 238.02891(3)
Krypton Kr 36 83.798(2) Vanadium V 23 50.9415(1)
Lanthanum La 57 138.90547(7) Xenon Xe 54 131.293(6)
Lawrencium2 Lr 103 (262) Ytterbium Yb 70 173.054(5)
Lead Pb 82 207.2(1) Yttrium Y 39 88.90585(2)
Lithium Li 3 [6.941(2)]1 Zinc Zn 30 65.38(2)
Lutetium Lu 71 174.9668(1) Zirconium Zr 40 91.224(2)
Magnesium Mg 12 24.3050(6) -2,3,4 112 (285)
Manganese Mn 25 54.938045(5) -2,3 113 (284)
Meitnerium2 Mt 109 (276) - 2,3 114 (287)
Mendelevium2 Md 101 (258) -2,3 115 (288)
Mercury Hg 80 200.59(2) -2,3 116 (293)
-2,3 118 (294)




This table shows the elements, their symbols, and the atomic weights of each element. The atomic weights are relative to the massA measure of the force required to impart unit acceleration to an object; mass is proportional to chemical amount, which represents the quantity of matter in an object. of the Carbon-12 atom 12C = 12 where 12C is a neutral atom in its ground nuclear and electronic state.

The highlighted elements are those which will occur most often in the study of general chemistry. These elements and their symbols are important to become familiar with and recognize.

1. The atomic weights of many elements vary depending on the origin of the sample and its treatment. One example of this is lithium. Commercially available lithium-containing materials have Li atomic weights in the range of 6.939 and 6.996. Uncertainties are given in parentheses following the last significant figureAny of the digits in a value that are known with certainty; all of the digits in a number correctly expressed in scientific notation. to which they are attributed.

2. Elements with no stable nuclideAn atom having a particular number of protons and neutrons; isotopes are a set of nuclides all with the same atomic number.; the value given is the atomic massThe average mass of the naturally occurring isotopes of an element, taking into account the different natural abundances of the isotopes. Expressed relative to the value of exactly 12 for carbon-12; also called atomic weight. number of the isotopeOne of two or more samples of an element whose atoms differ in the number of neutrons found in the nucleus. of the longest known half-lifeIn chemical kinetics, the time it takes for one half of the limiting reactant to be consumed. In nuclear chemistry, the time for half of a sample to undergo radioactive decay.. Three elements (Th, Pa, and U) have a characteristic terrestrial isotopic composition and the atomic weight is tabulated for these.

3. Elements not yet named

4. The name copernicium was proposed for element 112 in July 2009, but is not officially accepted by IUPAC at this time.


This table is from CoreChem:The Atomic Theory. Aspects of atomic weight are also discussed on CoreChem:Atomic Weights.