Question

What is the phenomenon of radioactivity? How many types are there of radioactive decay?

Hint:

Radioactivity is spontaneous emission of radiation from an unstable nucleus; the decay is of three kinds, alpha, beta and gamma.

Answer 1

Step 1: Define radioactivity.
Radioactivity is the phenomenon in which the unstable nucleus of a heavy atom disintegrates on its own (spontaneously) and emits radiation in the form of \(\alpha\)-particles, \(\beta\)-particles or \(\gamma\)-rays, turning into a more stable nucleus. It was discovered by Henri Becquerel in 1896.

Step 2: State its key features.
It is a nuclear property (not affected by temperature, pressure or chemical state), and it is a random, spontaneous process that goes on until the nucleus becomes stable.

Step 3: List the types of radioactive decay.
There are three types:
1. Alpha (\(\alpha\)) decay: the nucleus emits an \(\alpha\)-particle (a helium nucleus \(_2^4He\)); mass number decreases by 4 and atomic number by 2.
2. Beta (\(\beta\)) decay: the nucleus emits a \(\beta\)-particle (an electron); atomic number changes by 1 while mass number stays the same.
3. Gamma (\(\gamma\)) decay: the excited nucleus releases energy as high-energy \(\gamma\)-ray photons; neither mass number nor atomic number changes.
\[\boxed{\text{Three types: } \alpha,\ \beta,\ \gamma \text{ decay}}\]