Isotopes & Average Atomic Mass

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Presentation transcript:

Isotopes & Average Atomic Mass

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

Are these isotopes? Yes No

The average atomic mass of Carbon is 12. 011 amu The average atomic mass of Carbon is 12.011 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

Weighted Averages Ages: Find average age:

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

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 0.7577) + (37 x 0.2423) = 35.5 amu

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

M&M lab