Match the articles in  column I with column II.
 

	Column I		Column II
a	Electronic configuration of isotopes of hydrogen ${}_1{}^1\mathrm{H}$ and  ${}_1{}^2\mathrm{H}$:	i	K=2, L=8, M=8, N=2
b	Electronic configuration of isobars of ${}_{18}{}^{40}\mathrm{Ar}$	ii	K=1
c	Electronic configuration of isobars of  ${}_{20}{}^{40}\mathrm{Ca}$	iii	K=2, L=8, M=8

Atoms that contain variable numbers of neutrons, but the same number of protons are called isotopes. They differ in mass yet have the same atomic number. 

Since the electronic configuration of isotopes of hydrogen is K=1. 

The isobars are then atoms with various atomic numbers but the same mass number. 

The electronic configuration of argon is K=2, L=8, M=8 and calcium is K=2, L=8, M=8, N=2.