4.  Chlorine is a gaseous element. It’s symbol is Cl. Chlorine is a greenish yellow poisonous gas with a disagreeable, suffocating odour, it is more dense as the air. Chlorine belongs to Halogen family of elements.  Chlorine reacts with most metals, does not react well with Oxygen. Chlorine is a powerful oxidizing agent. Chlorine composes 0.14%of the earth’s crust

8.  Carbon is a colourless, odourless gas that is slightly soluble in water.  It is more dense than air and slightly acidic.  Carbon as a diamond can be used as jewellery, drill tips and for cutting tools.

9.  Silicon is not found in nature, but it is the most abundant element on the earth forming 25.7% of the earth’s crust.  Silicon is a brown/grey solid that has a high melting point, it is very hard and a semi- conductor of electricity.

10.  Silicon is used for computer chips, building materials  The manufacture of paper, china, cotton and textiles  For motors and transformers, water proofing fabrics and medical implants.

11.  Graphite can be used to make : lead pencils  Oil paints, lubricants  electrodes in electrolysis  brushes in electric motors and generators.

12.  Phosphorus is essential in plant and animal tissue in the formation of genetic material, DNA and energy storing.  It can be broken into two parts white and red phosphorus.  Phosphorus {white }is a white waxy, translucent solid that has a low melting point, soluble in organic solvents and is a non-conductor of electricity.  Phosphorous {red} is a dark opaque powder that has a high melting point, it is soluble on organic solvents and a non-conductor of electricity.

13.  Manufacture of safety matches, smoke bombs tracer bullets.  Manufacture of rust proofing iron and steel, manufacture of fertilisers.  Cleaning agents, water softener, cheese processing, manufactures of pesticides

14.  Nitrogen forms 78% of air by volume. It is also found in combined in nitrates and proteins  Nitrogen is a colourless. odourless gas that is insoluble in water, but has the same density as air.  Nitrogen combines with oxygen and hydrogen

15.  For the manufacture of light bulb,explosives,  Also to make laughing gas.