Write Lewis symbols for the following atoms and ions:
$\mathrm{S}$ and $\mathrm{S}^{2-} ; \mathrm{Al}$ and $\mathrm{Al}^{3+} ; \mathrm{H}$ and $\mathrm{H}^{-}$
(i) Sand $s^{2-}$
The number of valence electrons in sulphur is 6.
The Lewis dot symbol of sulphur (S) is : $\ddot{s}$ :
The dinegative charge infers that there will be two electrons more in addition to the six valence electrons. Hence, the Lewis dot symbol of $S^{2-}$ is $[\because{3}:{s}]^{2-}$.
(ii) $\mathrm{Al}$ and $\mathrm{Al}^{3+}$
The number of valence electrons in aluminium is 3 .
The Lewis dot symbol of aluminium (Al) is ${ }^{*} \mathrm{Al}^{\circ}$.
The tripositive charge on a species infers that it has donated its three electrons. Hence, the Lewis dot symbol is $[\mathrm{A}]^{3+}$.
(iii) $\mathrm{H}$ and $\mathrm{H}^{-}$
The number of valence electrons in hydrogen is 1 .
The Lewis dot symbol of hydrogen $(\mathrm{H})$ is $\mathrm{H}$.
The uninegative charge infers that there will be one electron more in addition to the one valence electron. Hence, the Lewis dot symbol is $[\ddot{H}]^{-}$.