Question

Assertion :The position of an element in periodic table after emission of one $\alpha$ and two $\beta -$ particles remains unchanged. Reason: Emission of one $\alpha$ and two $\beta -$ particles gives isotope of the element which acquires same position in periodic table.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Let us take an element ${}_{\text{x}}^{\text{y}}\text{A}$.

${}_x^{y}A\stackrel{-\alpha }{⟶}{}_{x-2}^{y-4}B\stackrel{-2\beta }{⟶}{}_x^{y-4}C$
Here we can see that after emission of one $\alpha$ and two $\beta -$ particles, atomic number and hence position of element remains unchanged. Further, the same atomic number indicates that it is an isotope of the element ${}_x^{y}A$ and isotopes are placed at one place in the periodic table. Hence assertion and reason are true and reason is the correct explanation of assertion.