Which of the following are identical in terms of their atomic number $(Z)$?
$(i)$ $Na$ and $Na^+$
$(ii)$ $F$ and $F^-$

The metal ion with total number of electrons same as $S^{2-}$ is

If the atomic weight of an element is $23$ times that of the lightest element and it has $11$ protons,then it contains

Nucleons are equal to :

When $\mathop a\limits^x U$ is converted into $\mathop b\limits^y P$,which of the following represents the correct decrease in the number of neutrons?

An element has an atomic weight of $40$ and its electronic configuration is $1s^2 2s^2 2p^6 3s^2 3p^6$. What are its atomic number and the number of neutrons?