Question

Observe the following statements regarding isotones :
i) ${}^{39}{K}_{19}$ and ${}^{40}C{A}_{20}$ are isotones
ii) Nuclides having different atomic numbers ($z$) and mass number ($A$) but same number of neutrons (n) are called Isotones
iii) ${}^{19}{F}_9$ and ${}^{23}N{A}_{11}$ are isotones .
The correct answer is

• A. i,ii and iii are correct
• B. i and ii are correct
• C. i and iii are correct
• D. ii and iii are correct

Answer 1

The correct option is B i and ii are correct

We know that when nuclides have same number of neutrons (N) but have different mass number (A) and protons number(Z) are called Isotones.

i) For ${}^{39}{K}_{19},Z=19,A=39,N=39-19=20$ and for ${}^{40}C{A}_{20},Z=20,A=40,N=40-20=20$

Since both nuclides have same neutrons number so they are isotones.

iii) For ${}^{19}{F}_9,Z=9,A=19,N=19-9=10$ and for ${}^{23}N{A}_{11},Z=11,A=23,N=23-11=12$

Since both nuclides have different neutrons number so they are not isotones.

Hence, statement i) and ii) are correct.