Question

Write Lewis symbols for the following atoms and ions: S and S2– ; Al and Al3+; H and H–

Answer 1

(i) S and S2–

The number of valence electrons in sulphur is 6.

The Lewis dot symbol of sulphur (S) is $\stackrel{..}{:S:}$ .

The dinegative charge infers that there will be two electrons more in addition to the six valence electrons. Hence, the Lewis dot symbol of S2– is ${\left[\underset{..}{\stackrel{..}{:S:}}\right]}^{2-}$ .

(ii) Al and Al ${}^3+$

The number of valence electrons in aluminium is 3.

The Lewis dot symbol of aluminium (Al) is: $\stackrel{.}{.Al.}$

The tripositive charge on a species infers that it has donated its three electrons. Hence, the Lewis dot symbol is: $[Al{]}^{+3}$

(iii) H and H–

The number of valence electrons in hydrogen is 1.

The Lewis dot symbol of hydrogen (H) is: $\stackrel{.}{H}$

The uninegative charge infers that there will be one electron more in addition to the one valence electron. Hence, the Lewis dot symbol is: $[H{]}^{+1}$