SAT II Chemistry : Atomic Mass

Study concepts, example questions & explanations for SAT II Chemistry

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Example Questions

Example Question #1 : Elements, Ions, And Isotopes

An atom of phosphorus has 15 protons, 16 neutrons, and 15 electrons. What is the atom's mass number?

Possible Answers:

Correct answer:


Protons and neutrons both have masses of approximately 1 amu, whereas the mass of an electron is negligible. Therefore, the mass number is equal to the number of protons and neutrons, which is 31.

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