Question

neon has 3 different isotopes, neon-20, neon-21, and neon-22. the first isotope has a mass 19.992 amu and an abundance of 90.60% . the second isotope (neon-21) has an abundance of 0.21%. the third isotope has a mass 21.991 amu and an abundance of 9.20%. what is the mass of the second isotope?

Answer 1

Isotopes

Mass atom of Neon: 20.1797 amu

Mass atom X = mass isotope 1 . % + mass isotope 2.% +.....

$\tt 20.1797=19.992\times 0.906+x\times 0.0021+21.991.0\times 0920\\\\x=20.846~amu$