16.18: Atomic Weights of the Elements
- Page ID
- 135885
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The atomic weight of any isotope of an element is referenced to 12C, which is assigned an exact atomic weight of 12. The atomic weight of an element, therefore, is calculated using the atomic weights of its isotopes and the known abundance of those isotopes. For some elements the isotopic abundance varies slightly from material- to-material such that the element’s atomic weight in any specific material falls within a range of possible value; this is the case for carbon, for which the range of atomic masses is reported as [12.0096, 12.0116]. For such elements, a conventional, or representative atomic weight often is reported, chosen such that it falls within the range with an uncertainty of \(\pm 1\) in the last reported digit; in the case of carbon, for example, the representative atomic weight is 12.011. The atomic weights reported here—most to five significant figures, but a few to just three or four significant figures—are taken from the IUPAC technical report (“Atomic Weights of the Elements 2011,” Pure Appl.Chem. 2013, 85, 1047–1078). Values in ( ) are uncertainties in the last significant figure quoted and values in [ ] are the mass number for the longest lived isotope for elements that have no stable isotopes. The atomic weights for the elements B, Br, C, Cl, H, Li, Mg, N, O, Si, S, Tl are representative values.
| At. No. | Symbol | Name | At. Wt. | At. No. | Symbol | Name | At. Wt. |
|---|---|---|---|---|---|---|---|
| 1 | H | hydrogen | 1.008 | 60 | Nd | neodymium | 144.24 |
| 2 | He | helium | 4.0026 | 61 | Pm | promethium | [145] |
| 3 | Li | lithium | 6.94 | 62 | Sm | samarium | 150.36(2) |
| 4 | Be | beryllium | 9.0122 | 63 | Eu | europium | 151.96 |
| 5 | B | boron | 10.81 | 64 | Gd | gadolinium | 157.25(3) |
| 6 | C | carbon | 12.011 | 65 | Tb | terbium | 158.93 |
| 7 | N | nitrogen | 14.007 | 66 | Dy | dysprosium | 162.50 |
| 8 | O | oxygen | 15.999 | 67 | Ho | holmium | 164.93 |
| 9 | F | fluorine | 18.998 | 68 | Er | erbium | 167.26 |
| 10 | Ne | neon | 20.180 | 69 | Tm | thulium | 168.93 |
| 11 | Na | sodium | 22.990 | 70 | Yb | ytterbium | 173.05 |
| 12 | Mg | magnesium | 24.305 | 71 | Lu | lutetium | 174.97 |
| 13 | Al | aluminum | 26.982 | 72 | Hf | halfnium | 178.49(2) |
| 14 | Si | silicon | 28.085 | 73 | Ta | tantalum | 180.95 |
| 15 | P | phosphorous | 30.974 | 74 | W | tungsten | 183.84 |
| 16 | S | sulfur | 32.06 | 75 | Re | rhenium | 186.21 |
| 17 | Cl | chlorine | 35.45 | 76 | Os | osmium | 190.23(3) |
| 18 | Ar | argon | 39.948 | 77 | Ir | iridium | 192.22 |
| 19 | K | potassium | 39.098 | 78 | Pt | platinum | 195.08 |
| 20 | Ca | calcium | 40.078(4) | 79 | Au | gold | 196.97 |
| 21 | Sc | scandium | 44.956 | 80 | Hg | mercury | 200.59 |
| 22 | Ti | titanium | 47.867 | 81 | Tl | thallium | 204.38 |
| 23 | V | vanadium | 50.942 | 82 | Pb | lead | 207.2 |
| 24 | Cr | chromium | 51.996 | 83 | Bi | bismuth | 208.98 |
| 25 | Mn | manganese | 54.938 | 84 | Po | polonium | [209] |
| 26 | Fe | iron | 55.845(2) | 85 | At | astatine | [210] |
| 27 | Co | cobalt | 58.933 | 86 | Rn | radon | [222] |
| 28 | Ni | nickel | 58.693 | 87 | Fr | francium | [223] |
| 29 | Cu | copper | 63.546(3) | 88 | Ra | radium | [226] |
| 30 | Zn | zinc | 65.38(2) | 89 | Ac | actinium | [227] |
| 31 | Ga | gallium | 69.723 | 90 | T | thoriium | 232.04 |
| 32 | Ge | germanium | 72.630 | 91 | Pa | protactinium | 231.04 |
| 33 | As | arsenic | 74.922 | 92 | U | uranium | 238.03 |
| 34 | Se | selenium | 78.96(3) | 93 | Np | neptunium | [237] |
| 35 | Br | bromine | 79.904 | 94 | Pu | plutonium | [244] |
| 36 | Kr | krypton | 83.798(2) | 95 | Am | americium | [243] |
| 37 | Rb | rubidium | 85.468 | 96 | Cm | curium | [247] |
| 38 | Sr | strontium | 87.62 | 97 | Bk | berkelium | [247] |
| 39 | Y | yttrium | 88.906 | 98 | Cf | californium | [251] |
| 40 | Zr | zirconium | 91.224(2) | 99 | Es | einsteinium | [252] |
| 41 | Nb | niobium | 92.906(2) | 100 | Fm | fermium | [257] |
| 42 | Mo | molybdenum | 95.96(2) | 101 | Md | mendelevium | [258] |
| 43 | Tc | technetium | [97] | 102 | No | nobelium | [259] |
| 44 | Ru | ruthenium | 101.07(2) | 103 | Lr | lawrencium | [262] |
| 45 | Rh | rhodium | 102.91 | 104 | Rf | futherfordium | [267] |
| 46 | Pa | palladium | 106.42 | 105 | Db | dubnium | [270] |
| 47 | Ag | silver | 107.87 | 106 | Sg | seaborgiuim | [271] |
| 48 | Cd | cadmium | 112.41 | 107 | Bh | bohrium | [270] |
| 49 | In | indium | 114.82 | 108 | Hs | hassium | [277] |
| 50 | Sn | tin | 118.71 | 109 | Mt | meitnerium | [276] |
| 51 | Sb | antimony | 121.76 | 110 | Ds | darmstadium | [281] |
| 52 | Te | tellurium | 127.60(3) | 111 | Rg | roentgenium | [282] |
| 53 | I | iodine | 126.90 | 112 | Cn | copernicium | [285] |
| 54 | Xe | xenon | 131.29 | 113 | Uut | ununtrium | [285] |
| 55 | Cs | cesium | 132.91 | 114 | Fl | flerovium | [289] |
| 56 | Ba | barium | 137.33 | 115 | Uup | ununpentium | [289] |
| 57 | La | lanthanum | 138.91 | 116 | Lv | livermorium | [293] |
| 58 | Ce | cerium | 140.12 | 117 | Uus | ununseptium | [294] |
| 59 | Pr | praseodymium | 140.91 | 118 | Uno | ununoctium | [294] |