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In most of Japanese high-school textbook it is written that Al,Zn,Sn and Pb are amphoteric element(in Japanese 両性元素）because they react both with strong acid and base.

For example Al reacts like below.

$\ce{2Al +2NaOH +6H2O->2Na[Al(OH)4] +3H2}$

$\ce{2Al + 6HCl-> 2AlCl3 + 3H2}$

It is true that these are reaction with acid or base with Al, but in these reactions Al is not acting as a base or an acid. Al is acting as a reductant.

https://goldbook.iupac.org/terms/view/A00306

In above IUPAC definition, it is written that "A chemical species that behaves both as an acid and as a base is called amphoteric.".

Since Al acts not as an acid or a base but as a reductant, I thought it is inappropriate to call the Al element itself as an amphoteric substance, although its oxide and hydroxide is amphoteric. Or are these reaction actually a kind of acid-base reactions?

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    $\begingroup$ They obviously use the term "amphoteric element" as an element reacting with both acid and bases. That somewhat overlaps with the element ability to form amphoteric compounds, typically oxides and hydroxides. But many compounds that are not usually considered amphoteric, becomes amphoteric in extreme conditions. $\endgroup$
    – Poutnik
    Commented Sep 26, 2022 at 9:51
  • $\begingroup$ "Amphoteric element" is definitely a term used in the past but I think its usage has become obsolete. pubs.acs.org/doi/pdf/10.1021/ed008p2126 $\endgroup$
    – Nilay Ghosh
    Commented Feb 28, 2023 at 11:10

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You are right, there is a problem in the textbook's description. Elements are not amphoteric, it is their oxides which are amphoteric. Zinc oxide, aluminum oxide, lead oxide will all dissolve in strong bases or strong acids. In the bases, we get correpsonding anions containing the metal which are called zincate, aluminate, and plumbate respectively. In the acids, we would get their corresponding cations.

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    $\begingroup$ Thank you! It seems Japanese ministry of education must learn more about chemistry. $\endgroup$
    – satoru kurita
    Commented Sep 26, 2022 at 3:09
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    $\begingroup$ It should be specified that : An amphoter is a substance which reacts with acids and bases, provided there is no change of oxidation numbers in the reaction. $\endgroup$
    – Maurice
    Commented Sep 26, 2022 at 12:42

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