If a nucleus loses 2 protons and 2 neutrons, what happens to its atomic number and mass number?

If a nucleus loses 2 protons and 2 neutrons, what happens to its atomic number and mass number?

• A. Atomic number decreases by 2, mass number decreases by 4
• B. Atomic number decreases by 4, mass number decreases by 2
• C. Atomic number decreases by 2, mass number remains the same
• D. Atomic number stays the same, mass number decreases by 4

Answer: (A)

The atomic number tells how many protons are in the nucleus, and the mass number is the total of protons and neutrons. If the nucleus loses 2 protons and 2 neutrons, the atomic number decreases by 2 (fewer protons) and the mass number decreases by 4 (four nucleons removed in total: two protons plus two neutrons). So you end up with an atomic number lower by 2 and a mass number lower by 4, reflecting both the change in identity (fewer protons) and the loss of four nucleons.

The atomic number tells how many protons are in the nucleus, and the mass number is the total of protons and neutrons. If the nucleus loses 2 protons and 2 neutrons, the atomic number decreases by 2 (fewer protons) and the mass number decreases by 4 (four nucleons removed in total: two protons plus two neutrons). So you end up with an atomic number lower by 2 and a mass number lower by 4, reflecting both the change in identity (fewer protons) and the loss of four nucleons.