Question

An element A decays into an element C by a two-step process:
$A\to B+H{e}_2^4$ and $B\to C+{2e}_{-1}^0$.Then

• A. A and C are isotopes
• B. A and C are isobars
• C. B and C are isotopes
• D. A and B are isobars

Answer 1

The correct option is A A and C are isotopes

Conservation of mass no. and charge holds true
$A\to B$
$Z_B=Z_A-2$
$M_B=M_A-4$
$B\to C+2e$
$Z_C=Z_B+2=Z_A$
$M_C=M_B=M_A-4$
Different mass, but same atomic No.
Therefore, A and C are isotopes.