What would be the electronic configuration of a positively charged sodium ion, `Na^(+)` ? What would be its atomic number ?

Explanation

The atomic number of sodium is 11. So, neutral sodium atom (Na) has 11 electrons in it.
(i) A positively charged sodium ion `(Na^(+))` is formed by the removal of 1 electron from a sodium atom. So, a sodium ion has `11 - = 10` electrons in it. Thus, the electronic configuration of a sodium ion will be `underset("2, 8")("K L")or2,8`
(ii) The atomic number of an element is equal to the number of protons in its atom. Since a sodium atom as well as a sodium ion contain the same number of protons, therefore, the atomic number of sodium ion is the smae as that of a sodium atom, which is 11.