Question

What happens to the
(i) atomic number,
(ii) mass number of an element when
(a) an "α-particle‘’, (b) a β-particle, and (c) γ radiation, is emitted?

Answer 1

Alpha ( $\alpha$) emission :
If a radioactive nucleus $X$ with mass number $A$and atomic number $Z$emits an $\alpha$-particle, the daughter nucleus Y has a mass number equal to $(A-4)$and atomic number equal to $(Z-2$).
${}_Z{X}^A\to {}_{z-2}{Y}^{A-4}+{}_{2}H{e}^4$
Conclusion:
(i) Atomic number $Z$ decreases by 2 units.
(ii) Mass number $A$ decreases by 4 units.
Beta $\beta$ emission: If a radioactive nucleus $X$with mass number $A$ and atomic number Z emits a beta $\beta$ particle to form a daughter nucleus $Y$with mass number $A$and atomic number $Z+1$, then the change can be represented as follows : ${}_Z{X}^A+z_{\ast 1}{Y}^A+{}_{-1}{e}^0$
Conclusion :
(i)Atomic number Z increases by 1 unit.
(ii)Mass number A remains constant.
Gamma $\gamma$ emission :
The γ-ray takes no mass and no electric charge from the nucleus i.e., no neutrons or protons are lost, hence the nucleus does not decay into a different nucleus.
${}_Z{X}^A+z_{\ast 1}{Y}^A+{}_{-1}{e}^0$
Conclusion :
(i)Atomic number Z remains constant.
(ii)Mass number A remains constant.