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• Aluminum (Al) is a member of the periodic table's group IIIA, having a valence electron configuration of\({\rm{3}}{{\rm{s}}^{\rm{2}}}{\rm{3}}{{\rm{p}}^{\rm{1}}}\).
• Amphoteric substances have the ability to act as both a base and an acid.

Under the appropriate conditions, the amphoteric character of \({\rm{Al}}{({\rm{OH}})_3}\)can be demonstrated by its behaviour as an acid or a basic.

When in the presence of an acid, such as \({\rm{HCl}},\;{\rm{Al}}{({\rm{OH}})_3}\), it works as a Bronsted-Lowry base, accepting the acid's protons. HCl protonates all three hydroxides in \({\rm{Al}}{({\rm{OH}})_3}\), resulting in the formation of \({\rm{AlC}}{{\rm{l}}_3}\)and water.

\({\rm{Al}}{({\rm{OH}})_3} + 3{\rm{HCl}} \to {\rm{AlC}}{{\rm{l}}_3} + 3{{\rm{H}}_2}{\rm{O}}\)

The electron deficient Al centre behaves as a Lewis acid in the presence of a base such as NaOH, accepting a pair of electrons to produce the equivalent salt.

\({\rm{Al}}{({\rm{OH}})_3} + {\rm{NaOH}} \to {\rm{NaAl}}{({\rm{OH}})_4}\)