Page 223 - Chemistry ICSE Class X
P. 223
Metallurgy 209
Let us say it Again
Classification of elements. All elements are classified into metals, nonmetals and metalloids.
Metals are the elements (except hydrogen) which show a tendency to lose electrons and form cations. Thus, metals
are electropositive elements.
Nonmetals are the elements which show a tendency to gain electrons and form anions. Thus, nonmetals are
electronegative elements.
The elements which behave like metals as well as nonmetals are called metalloids.
Alkali metals. Elements of Group 1 (or Group Ia) are called alkali metals. Li, Na, K, Rb, Cs and Fr are alkali metals.
Alkaline earth metals. Elements of Group 2 (or Group IIA) are called alkaline earth metals. Be, Mg, Ca, Sr, Ba and Ra are
alkaline earth metals.
Physical properties of metals. Metals are malleable, ductile, lustrous, good conductors of heat and electricity. Metals
are hard (except sodium and potassium) and strong. Most metals (except sodium and potassium) have high melting and
high boiling points.
All metals except mercury are solids. Mercury is the only metal which is liquid at room temperature.
Physical properties of nonmetals. The elements which have a tendency to gain electrons to form anions are called
nonmetals. Nonmetals are electronegative elements. Sulphur, phosphorus, carbon, oxygen are typical nonmetals.
Nonmetals are brittle, soft with low melting and low boiling points.
Nonmetals are nonconductors of electricity and heat, i.e. nonmetals are insulators.
Graphite is the only nonmetal which conducts heat and electricity.
Nonmetals may be solid, liquid or gaseous at ordinary temperature.
Nonmetals show allotropy.
The main allotropic forms of some nonmetals are listed below:
Carbon: Diamond, Graphite
Sulphur: Rhombic sulphur, Monoclinic sulphur, Plastic sulphur
Phosphorus: White (yellow) phosphorus, Red phosphorus
Chemical properties of metals. All metals combine with oxygen to form basic or amphoteric oxides.
Metals which are more electropositive than hydrogen displace hydrogen from water and from dilute acids.
The oxides of metals such as Na, K, Ca, Mg, etc. are basic in nature.
The oxides of metals such as Zn, Al, etc. are amphoteric.
Metals form ionic chlorides with chlorine.
Ore. The mineral from which a metal can be extracted on commercial scale is called an ore. Ores are classified on the
basis of the compound of the metal present in the ore, viz. oxide ores, carbonate ores, sulphate ores and halide ores.
Important ores of some common metals are,
Copper : Copper glance (Cu S), Copper pyrites (CuFeS ), Malachite (Cu(OH) .CuCO )
2
3
2
2
Aluminium : Bauxite (Al O .2H O)
2 3 2
Iron : Haematite (Fe O )
2 3
Zinc : Zincite (ZnO), Calamine (ZnCO ), Zinc blende (ZnS)
3
Gangue. Unwanted earthly material present in an ore is called gangue.
Flux. A substance which during smelting combines with the earthly impurities present in the ore to form a fusible slag
is called a flux.
Ore concentration. Ores are concentrated by using any of the following methods:
Hydraulic washing, Magnetic separation, Froth flotation process, Leaching process.
Sulphide ores are concentrated by froth flotation process.
