Metals and Non-metals

Elements are broadly classified as metals non-metals. Metals can be distinguished from non-metal on the basis of their physical properties like malleability ductility, lusture. Metals have tendency to lose electrons whereas non-metal have tendency to gain electrons. Thus, metals show electropositive character whereas non-metals show electronegative character.

Malleability and Ductile: Metals are malleable. They can be beaten into thin sheets. They are also ductile and can be drawn into wire. Non-metals are neither malleable nor ductile.

Metallic Lusture: Metals show metallic lusture while non-metals do not show any metallic lusture except I2.

Hardness: Metals are hard except Hg, Na. Non-metals are soft except except diamond.

Sonorous: Metals are sonorous (produce sound) while non-metals are not.

An ore is a mineral from which a metal can be profitably extracted from it. Metallurgy is the branch of science which deals with extraction of metals from its ores. Some of the non-metals are also found in free state in nature. For example, sulphur and carbon (as coal, graphite, diamond).

Chemical properties of metals and non-metal are different. Metal and non-metal both react with oxygen (air), water and acids.

Reaction with Oxygen: Metals form oxides which are basic in nature. Oxides of aluminium (Al2O3), zinc (ZnO), tin (SnO) and iron (Fe2O3) are amphoteric. They react with acids as well as with bases.

Reaction with acids: Generally metals react with acids to form salts and evolve H2. For example, Mg + 2HCl → MgCl2 + H2

Reaction with water to form base: 2Na + 2H2O → 2NaOH + H2

Al or Fe react with steam to form oxides. 3Fe + 4H2O → Fe3O4 + 4H2

Reaction with bases: Al, Sn and Zn react with common base. For example, Sn + 2NaOH + H2O → Na2SnO3 + 2H2

Corrosion: Oxygen reacts with metals to form oxides. Oxidation of metals is known corrosion. For example, rusting of iron

4Fe + xH2O + O2 → 2Fe2O3.xH2O

Presence of moisture and oxygen is necessary for corrosion. Corrosion can be prevented by (i) Painting (ii) oiling and greasing (iii) Galvanization (iv) Alloying.