$_{18}Ar^{40}$,$_{20}Ca^{40}$ and $_{19}K^{40}$ are

Which of the following species are isoelectronic species? $(i)$ $O^{2-}$,$(ii)$ $F^{-}$,$(iii)$ $Na^{+}$,$(iv)$ $Mg^{2+}$

Which of the following species are isoelectronic: $Na, Na^+, F^-, F$?

An atom is composed of protons,neutrons,and electrons. If the mass of a neutron is halved and the mass of an electron is doubled,what will be the change in the mass of the nucleus of $_6C^{12}$?

What are nucleons?

$A$ sodium cation $(Na^+)$ has a different number of electrons from which of the following species?