Question

Which of the following is a pair of isobar?

• A. ${}_7{N}^{15},{}_8{O}^{16}$
• B. ${}_6{C}^{13},{}_7{N}^{13}$
• C. ${}_6{C}^{13},{}_7{N}^{14}$
• D. ${}_7{N}^{13},{}_8{O}^{15}$

Answer 1

The correct option is B ${}_6{C}^{13},{}_7{N}^{13}$

Atoms of chemical elements having same atomic mass but a different atomic number are called Isobars. The sum of the number of protons and neutrons together form the atomic mass. Therefore, we can also say the number of nucleons present in the nucleus is equal to the atomic mass of an atom. It will have the same number of nucleons.

For $C_6^{13}$ and $N_7^{13}$ , the mass number(13) is same but atomic number is different. Therefore, they are a pair of isobars.

Hence, the correct option is $B$.