# What is the average atomic mass of an element composed of a series of isotopes, X, Y, Z with respective masses, 18.473*"amu", 19.962*"amu", 21.469*"amu", and respective abundances, X=28.812%, Y=28.757%...?

Feb 7, 2018

We take the weighted average ..... and get $20.15 \cdot \text{amu}$

#### Explanation:

$\text{Average atomic mass"={18.473_"X"xx28.812%+19.962_"Y"xx 28.757% +21.469_"Z" xx(100-28.812-28.757)%}*"amu}$

$\equiv 20.15 \cdot \text{amu}$...if I have done my 'rithmetic right...

How did I get the percentage abundance of $Z$?

And it is likely that we got the element neon. How did I know this?