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Non-Metals and Metalloids

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.
  1. Nitrous oxide(N2O) is used as laughing gas .
  2. 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 occursinfree 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