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Question 2.2: What is the mass number of an atom containing: (a) 58 proton...

What is the mass number of an atom containing:
(a) 58 protons, 58 electrons, and 78 neutrons?
(b) 17 protons, 17 electrons, and 20 neutrons?

Strategy
The mass number of an atom is the sum of the number of protons and
neutrons in its nucleus.

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(a) The mass number is 58 + 78 = 136.
(b) The mass number is 17 + 20 = 37.

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