IUPAC Periodic Table of the Elements and Isotopes

Standard atomic weights are the best estimates by IUPAC of atomic weights that are found in normal materials, which are terrestrial materials that are reasonably possible sources for elements and their compounds in commerce, industry, or science. They are determined using all stable isotopes and selected radioactive isotopes (having relatively long half-lives and characteristic terrestrial isotopic compositions). Isotopes are considered stable (non-radioactive) if evidence for radioactive decay has not been detected experimentally.

© IUPAC | This version is dated June 2019.

For the interactive version see ISOTOPESMATTER.COM

Element has two or moreisotopes that are used to

determine its atomic weight.Variations are well known,and the standard atomic

weight is given as lower andupper bounds within square

brackets, [ ].

Element has two or moreisotopes that are used to

determine its standard atomicweight. The isotopic

abundance and atomicweights vary in normal

materials, but upper andlower bounds of the standardatomic weight have not been

assigned by IUPAC.

Element has only one isotopethat is used to determine its

standard atomic weight.Thus, the standard atomicweight is invariant and is

given as a single value withan IUPAC evaluated

uncertainty.

Element has no standardatomic weight because all ofits isotopes are radioactiveand, in normal materials, no

isotope occurs with acharacteristic isotopic

abundance from which astandard atomic weight can

be determined.

hydrogen

H11.008[1.007 84, 1.008 11]

helium

He24.002 602(2)

lithium

Li36.94[6.938, 6.997]

beryllium

Be49.012 1831(5)

boron

B510.81[10.806, 10.821]

carbon

C612.011[12.0096, 12.0116]

nitrogen

N714.007[14.006 43, 14.007 28]

oxygen

O815.999[15.999 03, 15.999 77]

fluorine

F918.998 403 163(6)

neon

Ne1020.1797(6)

sodium

Na1122.989 769 28(2)

magnesium

Mg1224.305[24.304, 24.307]

aluminium

Al1326.981 5385(7)

silicon

Si1428.085[28.084, 28.086]

phosphorus

P1530.973 761 998(5)

sulfur

S1632.06[32.059, 32.076]

chlorine

Cl1735.45[35.446, 35.457]

argon

Ar1839.95[39.792, 39.963]

potassium

K1939.0983(1)

calcium

Ca2040.078(4)

scandium

Sc2144.955 908(5)

titanium

Ti2247.867(1)

vanadium

V2350.9415(1)

chromium

Cr2451.9961(6)

manganese

Mn2554.938 043(2)

iron

Fe2655.845(2)

cobalt

Co2758.933 194(4)

nickel

Ni2858.6934(4)

copper

Cu2963.546(3)

zinc

Zn3065.38(2)

gallium

Ga3169.723(1)

germanium

Ge3272.630(8)

arsenic

As3374.921 595(6)

selenium

Se3478.971(8)

bromine

Br3579.904[79.901, 79.907]

krypton

Kr3683.798(2)

rubidium

Rb3785.4678(3)

strontium

Sr3887.62(1)

yttrium

Y3988.905 84(2)

zirconium

Zr4091.224(2)

niobium

Nb4192.906 37(2)

molybdenum

Mo4295.95(1)

technetium

Tc43

ruthenium

Ru44101.07(2)

rhodium

Rh45102.905 49(2)

palladium

Pd46106.42(1)

silver

Ag47107.8682(2)

cadmium

Cd48112.414(4)

indium

In49114.818(1)

tin

Sn50118.710(7)

antimony

Sb51121.760(1)

tellurium

Te52127.60(3)

iodine

I53126.904 47(3)

xenon

Xe54131.293(6)

caesium

Cs55132.905 451 96(6)

barium

Ba56137.327(7)

hafnium

Hf72178.49(2)

tantalum

Ta73180.947 88(2)

tungsten

W74183.84(1)

rhenium

Re75186.207(1)

osmium

Os76190.23(3)

iridium

Ir77192.217(2)

platinum

Pt78195.084(9)

gold

Au79196.966 570(4)

mercury

Hg80200.592(3)

thallium

Tl81204.38[204.382, 204.385]

lead

Pb82207.2(1)

bismuth

Bi83208.980 40(1)

polonium

Po84

astatine

At85

radon

Rn86

francium

Fr87

radium

Ra88

rutherfordium

Rf104

dubnium

Db105

seaborgium

Sg106

bohrium

Bh107

hassium

Hs108

meitnerium

Mt109

darmstadtium

Ds110

roentgenium

Rg111

copernicium

Cn112

nihonium

Nh113

flerovium

Fl114

moscovium

Mc115

livermorium

Lv116

tennessine

Ts117

oganesson

Og118

lanthanum

La57138.905 47(7)

cerium

Ce58140.116(1)

praseodymium

Pr59140.907 66(1)

neodymium

Nd60144.242(3)

promethium

Pm61

samarium

Sm62150.36(2)

europium

Eu63151.964(1)

gadolinium

Gd64157.25(3)

terbium

Tb65158.925 354(8)

dysprosium

Dy66162.500(1)

holmium

Ho67164.930 328(7)

erbium

Er68167.259(3)

thulium

Tm69168.934 218(6)

ytterbium

Yb70173.045(10)

lutetium

Lu71174.9668(1)

actinium

Ac89

thorium

Th90232.0377(4)

protactinium

Pa91231.035 88(1)

uranium

U92238.028 91(3)

neptunium

Np93

plutonium

Pu94

americium

Am95

curium

Cm96

berkelium

Bk97

californium

Cf98

einsteinium

Es99

fermium

Fm100

mendelevium

Md101

nobelium

No102

lawrencium

Lr103