Question

How does nuclear decay affect the atomic number and the mass number?

Answer 1

Hint: A nucleus undergoing radioactive reaction is highly unstable. It decays into constituent particles and a daughter atom which is very stable. The nucleus can undergo three types of decay; alpha decay, beta decay and gamma decay. In all types of decays, the properties of the nucleus change by different rules.

Complete answer:
The nuclear decay is the process by which a nucleus breaks into a daughter nucleus and constituent particles. There are three types of nuclear decay; alpha decay, beta decay and gamma decay
In alpha decay, the nucleus emits an alpha particle due to which their atomic number decreases by two and the mass number decreases by four. Therefore,
$X_b^a\to X_{b-4}^{a-2}+\alpha$
Here, $a$ is the atomic number
$b$ is the mass number
$\alpha$ is the alpha particle
In beta decay, the nucleus emits a beta particle due to which their atomic number decreases by one and there is no change in its mass number. Therefore,
$X_b^a\to X_b^{a-1}+\beta$
Here, $\beta$ is the beta particle
In gamma decay, the nucleus emits gamma particles but no change in mass number or atomic number takes place.
Therefore, in alpha particle mass number and atomic number both change, in beta decay only the mass number changes while in gamma decay no change in mass number or atomic number takes place.

Note:
An alpha particle is a Helium like atom with a dual charge on it. Beta particle is an electron-like atom with a unit charge on it and gamma particles are electromagnetic rays. The daughter atom is more stable than the parent nucleus and hence has more binding energy than the parent atom.