An ordinary oxygen sample contains:

An element has an electronic configuration of $2, 8, 18, 1$. If its atomic weight is $63$,then how many neutrons will be present in its nucleus?

The difference between $_{17}Cl^{35}$ and $_{17}Cl^{37}$ is in the:

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.

The nuclides (a nuclide is the general name for any nuclear species) $_6C^{12}$,$_{26}Fe^{56}$,and $_{92}U^{238}$ have $12$,$56$,and $238$ nucleons respectively in their nuclei. The total number of nucleons in a nucleus is equal to:

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