The number of electrons and neutrons of an element is $18$ and $20$ respectively. Its mass number is

Calculate the number of protons, neutrons and electrons respectively in ${}^{14}_{7}N^{3-}$.

An atom has the electronic configuration of $1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^{10}, 4s^2 4p^5$. Its atomic weight is $80$. Its atomic number and the number of neutrons in its nucleus shall be

Which of the following is not a hydrogen-like species?

$_{20}X^{40}$ and $_{21}X^{40}$ are

The mass number of an anion,$X^{3-}$,is $14$. If there are $10$ electrons in the anion,the number of neutrons in the nucleus of an atom of the element $X$ is: