The spectrum of $He$ is expected to be similar to

Which of the following pairs represents isobars?

$Na^{+}$ ion is isoelectronic with

If the electronic configuration of a metal ion $M^{2+}$ is $2, 8, 14$ and its atomic mass is $56 \, a.m.u.$,then the number of neutrons in its nucleus is .....

Assertion : The sum of protons and neutrons is always different in isobars.
Reason : Isobars are atoms of different elements having same mass number but different atomic number.

Give the definition and examples of isobars and isotopes.