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Average Atomic MassIf there are 2 naturally occurring isotopes ofNeon includingNe-20 and Ne-22.
then the average mass of Neon atoms should be ___ amu.
Calculated as a weighted average of atoms in a sample of naturally occurring isotopes.
Why does the PT lists it as 20.18 amu?
A weighted average atomic mass is calculated from both themasses of each isotope and therelative abundance (%) of each isotope.
63Cu is 69% abundant
65Cu is 31% abundant
To which will theaverage mass be closer,63 or 65?
Average Atomic Mass
copper-63has a mass of 62.93 amu and natural abundance of 69.15%
copper-65has a mass of 64.93 amuand has a natural abundance of 30.85%
= (62.93)(0.6915) + (64.93)(0.3085)
= 63.55
Avg. Mass = (Mass1)(%) + (Mass2)(%) …
Calculating Average Atomic Mass
because…the weighted average atomic mass of neon from the PT is 20.18 amu.
neon-20 neon-22
Which isotope is in greater relative abundance in natural samples of neon?
1. If an unusually selected sample of sulfur contained 90.0% sulfur-32 and 10.0% sulfur-34, what would be its average atomic mass?
A. 32.2 amu
B. 32.9 amu
C. 33.5 amu
D. 34.2 amu
Quick Quiz!
= (32)(0.900) + (34)(0.100)
= 32.2
Avg. = (M1)(%) + (M2)(%)