Question

What is the effect on the atomic mass and the atomic number of a radioactive element, after the emission of an α-particle?

Answer 1

During the emission of an α-particle from the nucleus of a radioactive element, its atomic mass decreases by 4 and the atomic number also decreases by 2. If _ZX^A represents a radioactive element having atomic mass A and atomic number Z, then:

$${\phantom{A}}_{\phantom{\mathrm{Z}}}^{\phantom{}}{\phantom{A}}_{\phantom{2}\mathrm{Z}}^{\phantom{2}}\mathrm{X}{\phantom{A}}^{\mathrm{A}}\underset{{\phantom{A}}_{\phantom{2}}^{\phantom{}}{\phantom{A}}_{\phantom{2}2}^{\phantom{2}}\mathrm{He}{\phantom{A}}^4}{\overset{\mathrm{\alpha }\text{-}\mathrm{particles}}{\to }}{\phantom{A}}_{\phantom{\mathrm{Z}-2}}^{\phantom{}}{\phantom{A}}_{\phantom{2}\mathrm{Z}-2}^{\phantom{2}}\mathrm{Y}{\phantom{A}}^{\mathrm{A}-4}$$