Question

An element is represented by ${}_Z{X}^A$, where Z is atomic number which is also equal to number of proton, A is mass number and X is symbol of the element.
Mass number (A) = Number of protons (Z) + Number of neutrons.
Isotopes: Atoms having same number of proton
Isobar: Elements having same mass number
Isotones: Elements having same number of neutron (A-Z)

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.
$\therefore {}_6{C}^{13},{}_7{N}^{13}$ are pair of isobar