Important Notes on Non-Metals and Metalloids

In this article, we will discuss the Non-Metals and Metalloids. One-liner type question usually comes from this topic. Every year there is a question from this topic in Railways Exam.

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 the 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 a 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 the making of jewellery and cutting glass.

Graphite:

• Its an exception, it is a good conductor of heat and electricity.
• Used in the 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 the transport of perishable food material as it provides the 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 the free state.
• This element which also exhibits the characteristic of allotropy.
• This is  the second most abundant element in 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 exists most abundantly in the solid state in 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 an inert atmosphere in different metallurgical operation.
• Used as a 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 is why it does not occur in the free state.
• Phosphorus is an essential constituent 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 exists 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 the position of the double bond in unsaturated organic compounds.

Sulphur(S):

• Sulphur occurs in the free state in volcanic areas.
• Sulphur exists in five allotropic form.
• Sulphur is used in rubber industry for vulcanization of rubber.
• Sulphuric acid is also known as oil of vitriol or king of chemicals.
• Sulphuric acid is prepared by two processes i.e. lead chamber process and contact process.

Halogens:

• Halogens are highly reactive elements and therefore they do not exist in the 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 the 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 a bleaching agent.
• Reacts with water to form HCL and HCIO.
• Used as a 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 the free state but radon is not present in nature.
• In the atmosphere, argon is the most abundant noble gas but in universe, helium is the most abundant gas.
• The mixture of Helium and Oxygen is used for artificial breathing of Asthma patients and by sea drivers.
• Helium is used as a pressuring agent in rockets to expel liquid oxygen and liquid hydrogen.
• Neon is used in a neon discharge lamp and signs for advertising purposes.
• Xenon is also known as stranger gas and a combined mixture of xenon and krypton is used in high-intensity photographic flash tubes.
• Radon is used in the preparation of an ointment for the treatment of cancer.
• A mixture of argon and nitrogen is used in an 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 the 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