Isotopes / Avg atomic mass

Multiple Choice

Isotopes are atoms of the same element that have different numbers of....

• Protons

• Neutrons

• Electrons

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How many neutrons does Lithium-7 have?

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How many neutrons does phosphorus-31 have?

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How many neutrons does chlorine-37 have?

Multiple Choice

An element has two isotopes. The first has a mass of 40 and the second has a mass of 42. If the average is 41.9, which of the two isotopes is more abundant?

• 40

• 42

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An element has two isotopes. The first has a mass of 40 and is present 35% of the time, and the second has a mass of 42 and is present 65% of the time. What is the average mass?