State the speed of each of α, β and γ radiations.

A certain radioactive nucleus emits a particle that leaves it's mass number unchanged, but increases it's atomic number by one. Identify the particle and write it's symbol.

State whether the following nuclear disintegrations are allowed or not (star indicate an excited state). Give reason if it is not allowed.

(a) $_{Z}^{A}\text{X} \longrightarrow _{Z}^{A}\text{X} + \gamma$

(b) $_{Z}^{A}\text{X} \longrightarrow \space _{Z-2}^{ \space \space \space \space \space A}\text{X} + \space _{2}^{4}\text{He}$

Complete the following sentences:

(a) The mass number and atomic number of an element are not changed when it emits ……………

(b) The atomic number of a radioactive element is not changed when it emits ……………

(c) During the emission of a beta particle, the …………… number remains same.