Non Metals:
- Non-metal may be solid, liquid or gas.
- Bromine is the only liquid non metals.
- Non metals are the elements that do not have the properties of the metals.
- They are soft, non lustrous, brittle ,non sonorous and poor conductor of heat and electricity .e.g. carbon, hydrogen, helium, neon krypton etc.
Important Non metals
Carbon:
- Carbon belongs to the group 14 of the periodic table.
- Carbon occurs both in free state as well as in combined state.
- Carbon has two crystalline allotropes diamond and graphite.
Allotropes of Carbon:
Diamond:
- Diamond is the hardest substance and is the bad conductor of electricity.
- Diamond is the purest form of the Carbon
- Used in making of jewellery and cutting glass.
Graphite:
- Its an exception , it is a good conductor of heat and electricity.
- Used in nuclear reactor as a moderator.
Compounds of Carbon:
Carbon monoxide:
- It is colourless, odourless, neutral and highly poisonous gas in nature.
- Combines with haemoglobin to form Carboxyhaemoglobin, which is not able to absorb oxygen as result leads to suffocation
- Wood fire or coal fire in a closed room leads to the formation of the carbon monoxide which leads to the death of the persons in the rooms.
Carbon Dioxide:
- Occur in the air to the extent of 0.03-0.05 percent.
- Solid CO2 is known as dry ice.
- Dry ice is used is used in transport of perishable food material as it provides cold and inert atmosphere which helps in killing bacteria, fungi, modules etc.
- Carbon dioxide is used by the plants in the process of photosynthesis for the formation of oxygen.
- Carbides are the compound of carbon with metals or electro-negative elements.
Silicon(Si)
- Silicon occurs in nature in the form of sand but never found in free state.
- This is a non-metallic element which also exhibits the characteristic of allotropy.
- This is the second most abundant element on the earth crust after oxygen
- Used as a superconductor in making computer chips.
- Silicon carbide is an artificial diamond called carborendum.
- Silica is also called sand which exist most abundantly in solid state in the nature and used in the production of glass, cement etc.
- Quartz is a crystalline form of SiO2.
Nitrogen(N2) :
- Important constituent of air about 79% by volume.
- Used in the manufacturing of nitric acid, ammonia and other nitrogen compounds.
- As a refrigerant in liquid form.
- To provide inert atmosphere in different metallurgical operation.
- Used as preservative in the food packing.
Compounds of Nitrogen:
Ammonia:
- Most important compound of nitrogen.
- Prepared by Haber’s process.
- It is soluble in water and its aqueous solution is alkaline in nature.
- Used in refrigerator and manufacturing of fertilisers and explosives.
- Nitrous oxide(N2O) is used as laughing gas .
- The symbiotic bacteria present in the root nodules of leguminous plant convert the atmospheric nitrogen into compounds of nitrogen .e.g. Azobactor.
Phosphorus(P):
- It is highly reactive non metal that why it does not occurs in free state.
- Phosphorus is an essential constituents of bones, teeth, blood nerves and tissue.
- Bones contains 80% phosphorus.
Allotropes of phosphorus:
- White phosphorus:
- Red phosphorus
- Black phosphorus
- Scarlet phosphorus
- Violet phosphorus
Oxygen
- Oxygen exist in two allotropic form that is in most stable diatomic form(O2) and in less stable triatomic form (O3) ozone.
- Oxygen is the supporter of combustion but it is non-inflammable.
- Oxygen dissolved in blood in the form of oxyhaemoglobin.
- Liquid oxygen mixed with freshly divided carbon is used in place of dynamite in coal mining.
- Ozone is formed by the action of UV rays from the Sun on Oxygen and protects the living beings by not allowing UV rays to reach the earth.
- Ozone is also used as germicide and disinfectant for sterilizing water and for detecting position of double bond in unsaturated organic compounds.
Sulphur(S):
- Sulphur occurs in free state in volcanic areas.
- Suphur exists in five allotropic form.
- Sulphur is used in rubber industry for vulcanization of rubber.
- Sulphuric acid is also known as oil of vitrol or king of chemicals.
- Sulphuric acid is prepared by two process i.e. lead chamber process and contact process.
Halogens:
- Halogens are highly reactive elements and therefore they do not exist in free state but exist only in combined form.
- Halogens have highest electron affinity so they act as strong oxidising agent.
- Their oxidising power decreases from fluorine to iodine.
Chlorine(Cl2):
- Chlorine always present in combined state in nature in the form of chlorides .
- Chlorine was first discovered by Scheele by the action of hydrogen chloride on manganese dioxide.
- Chlorine is used as an bleaching agent.
- Reacts with water to form HCL and HCIO.
- Used as disinfectant and oxidising agent ,
Iodine:
- It is used as an antiseptic as tincture of Iodine.
- Used in the cure of Goitre.
- Turns starch solution blue.
Noble Gases:
- Helium, neon , argon, krypton , xenon and radon are known as inert gases or noble gases.
- These elements have completely filled valence shell and so these do not form chemical bonds.
- These are always found in free state but radon is not present in nature.
- In atmosphere argon is the most abundant noble gas but in universe helium is the most abundant gas.
- Mixture of Helium and Oxygen is used for artificial breathing of Asthama patients and by sea drivers.
- Helium is used as pressuring agent in rockets to expel liquid oxygen and liquid hydrogen.
- Neon is used in neon discharge lamp and signs for advertising purposes.
- Xenon is also known as stranger gas and combined mixture of xenon and krypton is used in high intensity photographic flash tubes.
- Radon is used in the preparation of ointment for the treatment of cancer.
- A mixture of argon and nitrogen is used in electric bulb.
- Krypton is used in high efficiency miner’s cap lamps.
Metalloids:
- They have properties of both metals and non-metals.
- Six commonly known metalloids are boron, silicon, germanium, arsenic, antimony and tellurium.
- Typical metalloids have a metallic appearance but they are brittle and only fair conductor of electricity.
- Metalloids and their compounds are used in the manufacturing of alloys , biological agents, flames retarders, glasses, optical storage