Which one of the following is the correct electronic configuration of sodium?

Find the valency of chlorine,sulphur,and magnesium.

If bromine atom is available in the form of,say,two isotopes $_{35}^{79}Br$ $(49.7 \%)$ and $_{35}^{81}Br$ $(50.3 \%),$ calculate the average atomic mass of bromine atom. (in $,u$)

Rutherford's alpha-particle scattering experiment was responsible for the discovery of

On the basis of Rutherford's model of an atom,which subatomic particle is present in the nucleus of an atom?

Name the three sub-atomic particles of an atom.