1. Isotopes & Average Atomic Mass

2. What are isotopes?
Atoms of the same element that have different numbers of neutrons and different atomic masses.

3. Are these isotopes?
Yes No

4. The average atomic mass of Carbon is 12. 011 amu
The average atomic mass of Carbon is amu. Which isotope of Carbon would you expect to find in nature the majority of the time?
Carbon - 12
Carbon - 13
Carbon - 14
They are all equally found in nature

5. Weighted Averages
Ages: Find average age:

6. What is average atomic mass?
The mass calculated when we take into account all of the isotopes that exist and the abundance (percentage) of each type.
Chlorine 35
Abundance = 24.23%
Abundance = 75.77%
Chlorine 37

7. How to calculate (35 x 0.7577) + (37 x 0.2423) = 35.5 amu Example:
Chlorine
75.77% - Cl 35
24.23% - Cl 37
Isotope
Number of Protons
Number of Neutrons
Cl – 35
Cl - 37
Step #1
Step #2
Predict: Average atomic mass based on masses and percentages: amu
Step #3
Calculate average mass:
(mass x percent) + (mass x percent) = average atomic
mass
(35 x ) + (37 x ) = amu

8. What is different between isotopes of the same element?
Atomic # only
Mass # only
# of protons only
# of neutrons only
Both atomic # and # of protons
Both mass # and # of neutrons
Both # of neutrons and # of protons

9. M&M lab