1. Now you try! Helium – 4 Oxygen – 16 Magnesium – 26 Isotope
Hyphen Notation
Atomic Number
Mass Number
Protons
Electrons
Neutrons
Nuclear Symbol
Helium-4
Oxygen-16
Magnesium-26
Helium – 4
Oxygen – 16
Magnesium – 26

2. Bohr Model of the Atom

3. Carbon-12 Carbon-13 Carbon-14
Examples
Carbon-12 Carbon-13 Carbon-14

4. Now you try!
Helium – 4
Oxygen – 16
Magnesium – 26

5. PRACTICE

6. B Average Atomic Mass A weighted average of an element’s isotopes.
Places an emphasis on isotopes with a larger abundance. 5 B
10.812
Boron

7. Calculating Average Atomic Mass
A.A.M.=(Mass 1*Percent1)+(Mass 2*Percent2)+ …

8. Calculating Average Atomic Mass
A.A.M.=(Mass 1*Percent1)+(Mass 2*Percent2)+ … Ex: There are two natural occurring isotopes of the element chlorine. Chlorine-35 is 75.8% abundant, while chlorine-37 is 24.2% abundant. Calculate their average atomic mass.

9. Calculating Average Atomic Mass
A.A.M.=(Mass 1*Percent1)+(Mass 2*Percent2)+ … Ex: Calculate the average atomic mass of zirconium given the following information:
Isotope
Abundance
Zirconium-90
51.5%
Zirconium-91
11.2%
Zirconium-92
17.2%
Zirconium-94
17.4%
Zirconium-96
2.8%

10. Calculating Average Atomic Mass
A.A.M.=(Mass 1*Percent1)+(Mass 2*Percent2)+ …
Ex: Use the data from the mass spectrum graph to determine the element’s average atomic mass.
Then, identify the element.

11. PRACTICE