Physics - Radioactivity

Radioactivity is a nuclear phenomenon; it is a spontaneous and random process by which an unstable nucleus emits radiations like $\alpha$, $\beta$, and $\gamma$ to reach a stable state.

The composition of an atom is represented as $_{Z}^{A}X$, where $A$ is the mass number (protons + neutrons) and $Z$ is the atomic number (protons).

$\alpha$-particles are helium nuclei ($_{2}^{4}He$) with a charge of $+2e$ and mass of $4\,u$. They have the highest ionizing power but the least penetrating power.

$\beta$-particles are fast-moving electrons ($_{-1}^{0}e$) emitted from the nucleus when a neutron converts into a proton: $_{0}^{1}n \rightarrow _{1}^{1}p + _{-1}^{0}e$.

$\gamma$-radiations are electromagnetic waves of very short wavelength (approx $10^{-13}\,m$). They have the highest penetrating power and travel at the speed of light ($c \approx 3 \times 10^8\,m/s$).

In $\alpha$-decay, the mass number $A$ decreases by $4$ and the atomic number $Z$ decreases by $2$.

In $\beta$-decay, the mass number $A$ remains unchanged and the atomic number $Z$ increases by $1$.

Isotopes are atoms of the same element having the same $Z$ but different $A$. Isobars have the same $A$ but different $Z$. Isotones have the same number of neutrons $(A - Z)$.