There are five amphoteric elements (metals) in the periodic table Be, Al, Zn, Sn, Pb. Also those elements oxides and hydroxides are amphoteric compounds. Amphoteric elements and compounds react with both acids and bases and give relevant products.
The ability to react as an acid or a base, is known as amphoterism.
In this tutorial,
First, we discuss about amphoteric behavior of amphoteric different elements. Then we study about other amphoteric compounds of transition metals. Then explain some questions of amphoteric properties and compounds.
All amphoteric elements are metals and they are located in s, p, d blocks.
Now we discuss about amphoteric metals behavior of Be, Al, Zn, Sn, Pb and their oxides.
Beryllium is a metal of alkaline earth metals. Beryllium reacts with HCl and give beryllium chloride ( BeCl2 ) and H2 gas. Also beryllium reacts with NaOH and give sodium berrylate (NaBeO2.2H2O or Na2[Be(OH)4] ) and hydrogen gas(H2).
Aluminium reacts with both acids and bases to show amphoteric properties.
Aluminium reacts with HCl acid and give aluminium chloride ( AlCl3 ) and hydrogen ( H2 ) gas. Aluminium reacts with NaOH and give NaAlO2 or Na+[Al(OH)4]- which are aqueous solutions.
Aluminium hydroxide ( Al(OH)3 ) is also an amphoteric compound.
Zinc reacts with both acids and bases to give products.
ZnO can react as either an acidic or basic oxide and it is therefore known as an amphoteric oxide. ZnO reacts with HCl(aq), NaOH(aq), Na2O(aq).
Zinc oxide ( ZnO ) reacts with and hydrochloric acid ( HCl ) and give zinc chloride ( ZnCl2).
Zinc oxide ( ZnO ) reacts with sodium hydroxide ( NaOH ) and produce sodium zincate ( Na2ZnO2 ).
Zinc oxide ( ZnO ) reacts as an acid with sodium oxide ( Na2O ) and forms the zincate ion [Zn(OH)4]2- complex ion. This reaction is formally equivalent to the reaction without water.
Zinc hydroxide ( Zn(OH)2 ) is an amphoteric compound and a white precipitate. It reacts with HCl(aq) acid and give zinc chloride ( ZnCl2 ) aqueous solution. Also Zn(OH)2 reacts with excess NaOH and forms Na2[Zn(OH)4].
Lead(Pb) react with HCl and forms lead chloride ( PbCl2(s) ) and hydrogen gas ( H2(g) ). But Pb does not dissolve in concentrated HCl because a surface coating of PbCl2. Pb slowly reacts with cold alkali and rapidly by hot alkali forming plumbates.
Tin(Sn) react with dilute HNO3 acid to form Sn(NO3)2, NH4NO3 and water. Sn react slowly with cold alkali, but with hot alkali Sn react rapidly for, stannates .
Tin reacts with sodium hydroxide to give Sodium stannate ( Na2[Sn(OH)6] )
Beryllium oxide, Beryllium hydroxide exhibits amphoteric behavior.
Some 3d metal compounds such as chromium hydroxide, chromium(III) oxide, ferric oxide has amphoteric characteristics.
Chromium hydroxide (Cr(OH)3) is an amphoteric compound and a green precipitate. When NaOH(aq) is added that precipitate dissolve and give to [Cr(OH)4] - (aq) solution. Cr(OH)3 reacts with acids.
Chromium(III) oxide (Cr2O3) is an amphoteric compound. It is green colour and reacts with both acids and bases.
Ferric oxide(Fe2O3) reacts with both acids and basic oxides
Below figure shows the summary of amphoteric compounds such as oxides, hydroxides and amphoteric metals.
Questions asked by students
Yes. All amphoteric elements are metals.
No. Alkali metals' hydroxides, oxides do not show amphoteric properties. Therefore NaOH is not an amphoteric compound.
Amphoteric compounds form complexes with water or alkalis. Also you have to know, Not only amphoteric compounds form complexes. If metal ion is capable of forming complexes, there is no need to be a complex compound to form coordination complexes. All transition metals form complex compounds.
Alkali metals have less ability to form complex xompounds due to their less charge (+1).
NO. Zinc is the only amphoteric 3d block element.
Related Tutorials of Amphoteric Compounds