Neon has two major isotopes, Neom-20 and Neon 22. Out of every 250 neon atoms, 225 will be Neon-20 (19.992 g/mol), and 25 will be Neon-22 (21.991 g/mol). What is the average atomic mass of Neon?

1 Answer
anor277
Nov 28, 2017

The average atomic mass is necessarily the weighted average of the individual isotopes...

Explanation:

And so we simply make this calculation.....

#Ne_"average atomic mass"={225/250xx19.992+25/250xx21.991}*g*mol^-1=21.192*g*mol^-1#.

This site quotes the average mass of neon as #20.1797(6)*g*mol^-1#. What did they consider that we did not?

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