SAT Subject Physics Practice Question 143: Answer and Explanation

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Question: 143

6. Compared to the parent nucleus, the daughter of a β decay has

A. the same mass number but a greater atomic number
B. the same mass number but a smaller atomic number
C. a smaller mass number but the same atomic number
D. a greater mass number but the same atomic number
E. None of the above

Correct Answer: A

Explanation:

In β decay, a neutron is transformed into a proton and an electron. Therefore, the total nucleon number (mass number) doesn’t change, but the number of protons (the atomic number) increases by one.

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