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4.2 Atomic Calculations- Notation and Average Atomic Mass
Nuclear Symbols and Hyphen Notation tell us the Symbol of the Element, the number of protons and the Mass Number (
Protons + Neutrons). You will need your Periodic Table to complete this worksheet.
PART A - Convert the following between Nuclear Symbols and Hyphen Notation.
17
8𝑂
Nuclear
Symbol
Hyphen
Notation
22
10𝑁 𝑒
15
7𝑁
O- 17
K - 41
Cl - 36
PART B - Find or calculate the number of protons, electrons and neutrons in each of the following neutral atoms:
Symbol
17
22
35
8𝑂
Protons
8
Neutrons
17 – 8 = 9
17𝐶𝑙
K - 41
10𝑁 𝑒
Cl - 36
Calculating Average Atomic Mass from Abundance of Isotopes and their Mass
Please See Examples on the Website
Calculate the Average Atomic Masses as stated below.
1. K has 2 abundant isotopes. They are K – 39 (abundance is 93.12%) and the remainder is K – 41 .
a. Calculate the % that is K -41. (You should know how to do this)
b. Calculate the Average Atomic Mass using the table given (39.14 amu)
%
Mass
Subtotal
K-39
K-41
TOTAL 
2. The natural abundance of Boron isotopes is : 19.9 % B-10 and 80.1% B – 11 Calculate the atomic mass of boron.
Create a table as shown in the example above. Include units with your numbers. (10.81 amu)
3. The natural abundance of Gallium isotopes is : 60.11 % Ga-69 and 39.89% Ga – 71. Calculate the atomic mass of
Gallium. . Include units with your numbers. (69.8 amu)
HERE ARE SOME MORE COMPLEX
4.
5.
6. CONCEPTUAL QUESTION - Silver has an atomic mass of 107.868 amu. Does any atom of any isotope of silver have a
mass of 107.868 amu? Explain why.
7. HERE IS A MORE CHALLENGING QUESTION REQUIRING SOME ALGEBRA
The atomic mass of Cu is 63.540 amu. It is composed of two isotopes, Cu-63 and Cu-65, with atomic masses of 62.930
and 64.928. What is the % abundance of these isotopes?
HINT 1 : IF you calculate one, you will know the other.
HINT 2: What is the relation between the two % abundances?
HINT 3: Use the following Equation: Atomic Mass = (% Cu-63 x mass Cu-63) + (% Cu-65 x mass Cu-65)
Solution: Cu – 65 is 27% & Cu – 63 is 73%