Electronic configuration of the outermost shell of the atoms of some element are givenn below. From these identify the element and write their atomic numbers.
(1) `3s^(2)`
(2) `3p^(4)`.(3) `2p^(4)`.

Explanation

(1) Electronic configuration of the atom: `1s^(2)2s^(2)2p^(6)3s^(2)`
`therefore` Total number of electrons=12=number of protons=atomic number.
So, the element is magnesium (Mg). It has a valency of 2 because it can donate two electrons from the outermost shell to attain stable inert gas like electronic configuration.
(2) Electronic config, of the atom: `1s^(2)2s^(2)2p^(6)3s^(2)3p^(4)`
`therefore` Total number of electrons=16=number of protons=atomic number.
So, the element is sulphur (S), it has the valency 2 because it can gain two electrons in the outermost shell to attain inert gas like electronic configuration.
(2) Electronic config. of the atom : `1s^(2)2s^(2)2p^(6)3s^(2)3p^(4)`
`therefore`total number of electrons=16= Number of protons=atomic number.
So, the element is sulphur (S). it has the valency 2 because it can gain two electrons in the outermost shell to attain inert gas like electronic configuration.
(3) Electronic configuration of the atom: `1s^(2)2s^(2)2p^(4)`
`therefore`Number of electrons=8=number of protons=atomic number.
so, the element is oxygen (O). it has a valencey of 2 because it can gain two electrons in the outermost shell to attain inert gas like electronic configuration.