Elements are broadly classified as metals nonmetals. 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.
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 like 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. Certain oxides of metals show both the properties acidic as well as basic. For example, ZnO and Al2O3.
Metals
- Metals are malleable. They can be beaten into thin sheets. They are also ductile and can be drawn into wire.
- show metallic lusture.
- Hard except Hg, Na
- Solid and liquid states
- Sonorous (produce sound)
- High density
- Good conductor of electricity
Non-Metals
- Non-metals are neither malleable nor ductile. For e.g. coal, (carbon) and sulphur.
- Do not show any metallic lusture except I2.
- Soft except diamond
- Solid, liquid and gas
- Non-sonorous
- Low density
- Bad conductor of electricity
Chemical Properties of Metals
1. Reaction with Oxygen: Form oxides which are basic in nature.
Oxides of aluminium (Al2O3), zinc (ZnO), tin (SnO) and iron (Fe2O3) are amphoteric. React with acids as well as with bases.
2. Reaction with acids: Generally metals react with acids to form salts and evolved H2.
Mg + 2HCl → MgCl2 + H2
3. Reaction with water to form base
2Na + 2H2O → 2NaOH + H2
Al or Fe react with steam to form oxides
3Fe + 4H2O → Fe3O4 + 4H2
4. Reaction with bases
Al, Sn and Zn react with common base
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.