Question

question 20 (1 point)
when a neutron is emitted from an unstable nucleus, the atomic mass number of the
nucleus

increases by 1.

decreases by 1.

does not change.

none of the given answers

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Explanation:

The atomic mass number of a nucleus is the sum of the number of protons and neutrons in it. A neutron has a mass number of 1 (since its mass is approximately 1 atomic mass unit, and it contributes to the mass number). When a neutron is emitted from the nucleus, the number of neutrons decreases by 1. Since the mass number is protons + neutrons, and only the neutron count (which contributes 1 to the mass number) is reduced by 1, the atomic mass number decreases by 1.

Answer:

B. decreases by 1.