Question

What is the phenomenon of radioactivity?

Hint:

Think of the spontaneous break-up of an unstable heavy nucleus emitting alpha, beta and gamma rays.

Answer 1

Step 1: State the definition.
Radioactivity is the phenomenon of the spontaneous disintegration of the unstable nucleus of a heavy atom, during which it emits radiation and changes into a new (daughter) nucleus. It was discovered by Henri Becquerel in 1896.

Step 2: List the emitted radiations.
An unstable nucleus can emit three types of radiation:
1. Alpha \((\alpha)\) particles, which are helium nuclei \(({}_{2}^{4}\text{He})\).
2. Beta \((\beta)\) particles, which are fast-moving electrons (or positrons).
3. Gamma \((\gamma)\) rays, which are high-energy electromagnetic waves.

Step 3: Note its key features.
Radioactivity is a purely nuclear process. It is spontaneous and random, and it is not affected by external physical conditions such as temperature, pressure, or chemical combination. It occurs mainly in nuclei with atomic number greater than 82.

Result: Radioactivity is the spontaneous emission of \(\alpha\), \(\beta\), or \(\gamma\) radiation by an unstable nucleus as it transforms into a more stable nucleus.