Question

What kind of change takes place in a nucleus when a β-particle is emitted? Express it by an equation. State whether
(a) atomic number, and
(b) mass number are conserved in a radioactive β-decay?

Answer 1

When an unstable nucleus contains neutrons more than the protons, a neutron may change into a proton by emitting an electron. This electron emitted from the nucleus at a high speed is called a beta particle.
${}^{{}_1^0\text{n}}\to {}^{{}_1^1\text{p}}{+}^{{}_{-1}^0\text{e}}$
On emitting a β-particle, the number of nucleons in the nucleus (or mass number) remains same, but the number of neutrons is decreased by one and the number of protons is increased by one.
(a) Atomic number Z is increased by 1.
(a) Mass number remains unchanged.