Amphoteric metals and their properties

Amphoteric metals are simple substances that are similar in structure, chemical and physical properties to the metal group of elements. By themselves, metals can not exhibit amphoteric properties, unlike their compounds. For example, oxides and hydroxides of some metals have a dual chemical nature - under certain conditions they behave like acids, while in others they have the properties of alkalis.

The main amphoteric metals are aluminum, zinc, chromium, iron. To the same group of elements, beryllium and strontium can be included.

What is amphoricity?

For the first time this property was discovered long ago. And the term "amphoteric elements" was introduced into science in 1814 by the famous chemists L. Tenar and J. Gay-Lussac. In those days, chemical compounds were divided into groups that corresponded to their basic properties during the reactions.

Nevertheless, a group of oxides and bases possessed dual abilities. In some conditions such substances behaved as alkalis, in others, on the contrary, they acted as acids. This is how the term "amphotericity" arose. For such chemicals, the behavior during the acid-base reaction depends on the conditions of its conduct, the nature of the reagents involved, and also on the properties of the solvent.

It is interesting that in natural conditions amphoteric metals can interact with both alkali and with acid. For example, during the reaction of aluminum with sulfate acid , aluminum sulfate forms. And the reaction of the same metal with concentrated alkali forms a complex salt.

Amphoteric bases and their basic properties

Under normal conditions, these are solids. They practically do not dissolve in water and are considered to be rather weak electrolytes.

The main method for obtaining such bases is the reaction of a metal salt with a small amount of alkali. The precipitation reaction must be carried out slowly and carefully. For example, in the preparation of zinc hydroxide in a tube with zinc chloride carefully, add caustic drops. Each time you need to shake the container lightly to see the white sediment of the metal on the bottom of the dishes.

With acids and acid oxides, amphoteric substances react like bases. For example, the reaction of zinc hydroxide with hydrochloric acid produces zinc chloride.

But during reactions with bases, amphoteric bases behave like acids.

In addition, with strong heating, the amphoteric hydroxides decompose to form the corresponding amphoteric oxide and water.

The most common amphoteric metals: a brief description

Zinc refers to the group of amphoteric elements. And although the alloys of this substance were widely used even in ancient civilizations, in its pure form it could be separated only in 1746.

Pure metal is a brittle enough substance of bluish color. In air, zinc is rapidly oxidized - its surface dims and is covered with a thin film of oxide.

In nature, zinc exists mainly in the form of minerals - zincites, smithsonites, calamites. The most famous substance is zinc blende, which consists of zinc sulphide. The largest deposits of this mineral are found in Bolivia and Australia.

Aluminum is today considered the most common metal on the planet. Its alloys have been used for many centuries, and in 1825 the substance was isolated in pure form.

Pure aluminum is a light silvery metal. It is easy to machine and cast. This element has a high electrical and thermal conductivity. In addition, this metal is resistant to corrosion. The fact is that its surface is covered with a thin, but very resistant oxide film.

Today, aluminum is widely used in industry.