Why is the atomic weight of bromine listed on the periodic table not a whole number?

1 Answer
anor277
May 23, 2018

Because it reflects the isotopic abundance of bromine....

Explanation:

All the elements have an envelope of isotopes, and the atomic mass quoted on the Periodic Table is the WEIGHTED AVERAGE of the individual isotopes...

To a first approximation bromine consists of TWO isotopes: #51%# #""^79Br#, and #49%# #""^81Br#. The weighted average of the isotopes gives the quoted atomic mass...

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