The relative abundance of naturally occurring isotopes of neon is as follows:

²⁰Ne = 90.51%, ²¹Ne = 0.27%, ²²Ne = 9.22%

What is the average atomic mass of neon?

The average atomic mass of an element can be calculated by the formula:

$\frac{Atomic mass of isotope 1 X \% of occurence +Atomic mass of isotope 2 X \% of occurence}{100}$

The average atomic mass of neon =

$$\begin{gathered} =\frac{(20\times 90.51)+(21\times 0.27)+(22\times 9.22)}{100} \\ =20.19 u \end{gathered}$$