Question

When ${}_{92}{U}^{238}$ undergoes an $\alpha$-particle decay then incorrect option for daughter nuclei is:

• A. isodiapher species is formed
• B. group number in periodic table decreases
• C. mass number decrease by 4
• D. $n/p$ ratio increases

Answer 1

Answer: (B)

group number in periodic table decreases

After $\alpha$ decay, the daughter nuclide contains two fewer protons and two fewer neutrons than the parent. So n/ p ratio also increases.

Thus $\alpha$-particle emission produces a daughter nucleus with a mass number $A-4$ and a nuclear charge $Z-2$ compared to the parent nucleus.

${}_{92}{U}^{238}{\to }_{90}T{h}^{234}{+}_{2}H{e}^4$

Thus, $uranium-238$ decays through $\alpha$-particle emission to form $thorium-234$. Both of these elements are $actinides$ belongs to the $3^{rd}$ group of periodic table. Thus the group number in periodic table remains same.