The number of electrons in $[_{19}^{40}K]^{-1}$ is

The electronic configuration of a dipositive ion $M^{2+}$ is $2, 8, 14$ and its atomic mass is $56$. The number of neutrons in the nucleus would be :

Match the following species with the correct number of electrons present in them:

Species	Number of Electrons
$(i) Be^{2+}$	$(a) 0$
$(ii) H^{+}$	$(b) 10$
$(iii) Na^{+}$	$(c) 2$
$(iv) Mg^{+}$	$(d) 11$

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.

Which of the following pairs involves isoelectronic ions?

Which of the following has an isotopic number (neutron number) equal to that in $_{13}^{27}Al$?