Out of 200 neon atoms, 170 will be neon-20 (19.992 amu) and 30 will be neon-22 (21.991 amu). What is the average atomic mass of neon?

average atomic mass = 20.29185 amu

Explanation:

given data

neon atom = 200

170 atom = 20 (19.992 amu)

30 atom = 22 (21.991 amu)

to find out

average atomic mass

solution

we know that average atomic mass formula that is

average atomic mass = Σabundance (%) * exact mass ... 1

here we know that neon two major isotopes is Neon 20, Neon 22

abundance 1 = 170 / 200

abundance 2 = 30 / 200

exact mass 1 = 19.992 amu

exact mass 2 = 21.991 amu

so

average atomic mass = 170/200 * 19.992 + 30/200 * 21.991

average atomic mass = 20.29185 amu