average atomic mass. what does the atomic mass tell us on the periodic table?
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Average atomic Mass
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What does the atomic mass tell us on the Periodic
table?
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Atomic Mass
Weighted average of element’s natural isotopes
Some isotopes are more abundant than others….
SO atomic mass leans towards more abundant mass
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How do we calculate atomic mass?
1) Masses of Isotopes
2) Natural abundance of each isotope usually a percentage
Average atomic mass = mass contributed by all isotopes Fraction of abundance (isotope mass) = mass from a
particular isotope
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Example 1Neon has 3 natural isotopes.
Ne-20 (90.51%, 19.99244 u)
Ne-21 (0.27%, 20.99395 u)
Ne-22 (9.22%, 21.99138 u)
What is the weighted average atomic mass for Ne?
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Example 2: A certain metallic element has two stable isotopes: M-45 and M-48. Given that the atomic weights are 45.0010 and 48.0014, respectively, what is the percent abundance of the lighter isotope if the average atomic weight of M is 47.2002?
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Example 3: Calculate the atomic weight of chlorine if 75.77% of the atoms have a mass of 34.97 amu and 24.23% have a mass of 36.97 amu.