Question

During α-emission:

Options

• the mass number and atomic number of an atom decrease by 2 amu.

• the mass number decreases by 4 amu and atomic number decreases by 2 amu.

• the mass number remains unchanged, but atomic number decreases by 2 amu.

• the mass number decreases by 4 amu and atomic number remains unchanged.

Answer 1

The mass number decreases by 4 amu and atomic number decreases by 2 amu.

Explanation:

An α-particle is a helium nucleus containing 2 protons and 2 neutrons. So, the emission of one α-particle removes 4 nucleons from the nucleus; the mass number decreases by 4, and the atomic number decreases by 2.