Question

The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resultant daughter particle is an :

• A. isotope of parent
• B. isobar of parent
• C. isomer of parent
• D. isotone of parent

Answer 1

Answer: (A)

isotope of parent

$\alpha -$decay-

$Z^{X^A}\stackrel{\alpha }{\to }{Z-2}^{X^{A-4}}$

$\beta -$decay-

$Z^{X^A}\stackrel{\beta }{\to }{Z+1}^{X^A}$

$\Rightarrow$For each $\alpha$ particle there is a decrease in atomic number by 2 and atomic mass by 4.

$\Rightarrow$ For each ${\beta }^{-}$ particle there is an increase in atomic number by 1 and no change in atomic mass.

For the given,

No. of ${\beta }^{-}$ particles = 2(No. of $\alpha$ particles emitted)

Hence, there will be no change in atomic number but the atomic mass will change in the given radioactive decay.

$\therefore$ The resulting daughter is an isotope of parent.

Hence, option A is correct.