Question

Which of the following are pairs of isotones?

• A. $C{l}^{37}$ and $K^{39}$
• B. $N^{15}$ and $O^{16}$
• C. $G{e}^{76}$ and $S{e}^{76}$
• D. Both A and B

Answer 1

The correct option is D Both A and B

Isotones have same number of neutrons.
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Number of neutrons for $K^{39}=A-Z=39-19=20$
Number of neutrons for $C{l}^{37}=A-Z=37-17=20$

Number of neutrons for $O^{16}=A-Z=16-8=8$
Number of neutrons for $N^{15}=A-Z=15-7=8$

Number of neutrons for $G{e}^{73}=A-Z=73-32=41$
Number of neutrons for $S{e}^{76}=A-Z=76-34=32$

Hence, $a$ and $b$ are pairs of isotones.