Amphoteric metals and their properties

Amphoteric metals are simple substances,which in structure, chemical and physical properties are similar 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 foundlong. 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 possesseddual 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 amphotericmetals can interact with both alkali and acid. For example, during the reaction of aluminum with sulfate acid, aluminum sulfate forms. And when the same metal reacts with concentrated alkali, a complex salt is formed.

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 of obtaining such bases isreaction of a metal salt with a small amount of alkali. The precipitation reaction must be carried out slowly and carefully. For example, when zinc hydroxide is prepared into a zinc chloride tube, carefully add caustic soda to the tube. Each time you need to slightly shake the container to see the white sediment of the metal on the bottom of the dishes.

With acids and acidic 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 belongs 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 fairly brittle substance of bluish color. In air, zinc rapidly oxidizes - its surface dims and is covered with a thin film of oxide.

In nature, zinc exists predominantly in the formminerals - 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 today is considered the most common metal on the planet. Its alloys have been used for many centuries, and in 1825 the substance was isolated in its pure form.

Pure aluminum is a light metalsilver color. 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.