Naturally occurring neon exists as three isotopes. 90.51% is ne-20 with a mass of 19.99 amu, 0.27% is ne-21 with a mass of 20.99 amu, and 9.22% is ne-22 with a mass of 21.99 amu. what is the atomic mass of neon?

The atomic mass of an element is the average relative mass of its atoms as compared with an atom of carbon-12 whose mass is taken as 12. In terms of percentages of different isotopes, the average atomic mass can be determined as follows: = ∑(X )/100. Where, is the percentage abundance of isotope with atomic number .

So, average atomic mass of neon = = 20.177 amu.

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