Non - Metals | General Awareness for SSC CGL PDF Download

Non-Metals

• Non-metals can exist in solid, liquid, or gaseous states, with bromine being the only liquid non-metal.
• Key characteristics of non-metals include being soft, non-lustrous, brittle, non-sonorous, and poor conductors of heat and electricity.
• They generally have low melting and boiling points and form oxides with oxygen that are typically acidic.
• Examples include noble gases such as helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe), as well as p-block elements like chlorine (Cl₂), bromine (Br₂), and phosphorus (P).

Carbon (C)

Carbon is a group 14 (IV A) element in the periodic table and occurs in both free and combined states. In its free state, carbon is found as coal, diamond, and graphite, while in its combined state, it exists in carbonates, carbon dioxide, and petroleum. Carbon has two main crystalline allotropes: diamond and graphite.

Allotropes of Carbon:

• Diamond: The purest form of carbon, it is the hardest known substance and a poor conductor of electricity. It is used in jewelry, glass cutting, and as an abrasive.
• Graphite: Produced artificially by the Acheson process, graphite is a good conductor of heat and electricity. It is used in nuclear reactors as a moderator, as a dry lubricant, in electrodes, pencils, and crucibles.
• Fullerene (C₆₀): Resembling a soccer ball, fullerene contains 20 six-membered and 12 five-membered rings of carbon atoms. It acts as an excellent lubricant and its alkali metal compounds are superconducting at temperatures between 10-40 K.
• Graphene: An allotrope of carbon with a one-atom-thick planar sheet structure, graphene has a honeycomb crystal lattice. Discovered by Hanns-Peter Boehm in 1962, it is known for its exceptional conductivity and strength, making it suitable for use in touch screens, LCDs, and LEDs.

Compounds of Carbon:

• Carbon Monoxide (CO): A colorless, odorless, and highly poisonous gas that binds with hemoglobin to form carboxyhemoglobin, preventing oxygen absorption and causing suffocation (asphyxia). Low-level exposure leads to headaches and drowsiness, while high-level exposure can be fatal.
• Carbon Dioxide (CO₂): Present in the air at 0.03-0.05%, CO₂ is found in caves, mines, and volcanoes, and is released from the combustion of carbon materials and respiration. Solid CO₂, known as dry ice, is used for refrigeration and transporting perishable foods. CO₂ is crucial in photosynthesis, where green plants convert it into glucose, releasing oxygen.
• Carbides: Compounds of carbon with metals or electronegative elements. Methanides (containing C^4- ions) produce methane upon hydrolysis, while acetylides (containing C₂²⁻ ions) produce acetylene.

Silicon (Si)

Silicon is abundant in nature, found in sand and stone but never in a free state. It exhibits allotropy and is the second most abundant element in the Earth's crust (26%). Pure silicon is used in semiconductors, computer chips, acid-resistant steel, silica gel, and more.

Compounds of Silicon:

• Silicon Carbide: Known as carborundum, it is an artificial diamond.
• Silica (SiO₂): Commonly known as sand, it is used in glass and cement production. Quartz is a crystalline form of SiO₂.

Nitrogen (N₂)

Nitrogen constitutes 79% of the air and is vital for plant and animal proteins. It is colorless, odorless, non-poisonous, and chemically inert. Found in nitrates and ammonium salts, nitrogen is used in manufacturing nitric acid, ammonia, and as a refrigerant.

Compounds of Nitrogen:

• Ammonia (NH₃): Produced commercially via the Haber process, ammonia is a colorless gas with a pungent odor, used in refrigeration, fertilizers, and explosives.
• Nitrogen Fixation: Atmospheric nitrogen is converted into nitrates by lightning or bacteria, essential for plant growth.
• Nitrogen Cycle: Involves converting atmospheric nitrogen into compounds usable by plants and animals, then back into nitrogen gas by bacteria.

Phosphorus (P)

Phosphorus is highly reactive and found only in combined states like phosphates. It is essential for bones, teeth, blood, and nerve tissues.

Allotropes of Phosphorus:

• White Phosphorus: The most common and chemically reactive form.
• Red, Black, Scarlet, and Violet Phosphorus: Other allotropes with varying properties.

Compounds of Phosphorus:

• Phosphine (PH₃): A colorless, toxic gas with a rotten fish odor, used in smoke screens and warfare.

Oxygen (O₂)

Oxygen is a crucial component of the atmosphere, comprising 21% by volume, and is also present in oceans and the Earth's crust. Most atmospheric oxygen is produced through the photosynthesis of green plants.

Molecular Forms of Oxygen:

• Dioxygen (O₂): This is the most stable and common form, characterized by its colorless, odorless, and tasteless properties. Although non-flammable, it supports combustion.
• Ozone (O₃): This less stable, triatomic form is created in the upper atmosphere when UV rays from the sun interact with diatomic oxygen. Ozone protects life on Earth by blocking UV radiation. However, chlorofluorocarbons (CFCs) can deplete this ozone layer.

Uses of Oxygen:

• Essential for all aerobic organisms, oxygen is inhaled and transported by the blood as oxyhemoglobin, facilitating cellular metabolic processes.
• Used in life-support systems for hospitals, underwater diving, mining, and mountaineering.
• In liquid form, combined with finely divided carbon, it serves as an alternative to dynamite in coal mining.

Ozone Uses:

• Acts as a bleaching agent for oils, flour, ivory, and delicate fabrics due to its oxidizing properties.
• Used as a germicide, disinfectant, and for sterilizing water and detecting double bonds in organic compounds.

Sulphur (S)

Sulphur is found in volcanic regions like Sicily, Louisiana, Japan, and Mexico, and also in combined states such as sulphides and sulphates. Organic compounds from plants and animals, including onions, garlic, eggs, proteins, and wool, contain sulphur.

Allotropes of Sulphur:

• Rhombic Sulphur: The most stable form at room temperature, it transitions to this form from other allotropes over time.
• Monoclinic Sulphur: Also known as prismatic sulphur, this form is stable at higher temperatures.
• Plastic Sulphur, Milk of Sulphur, and Colloidal Sulphur: Other forms of sulphur with distinct properties.

Sulphur Properties:

• Melts at 114°C to a pale yellow liquid, becomes thicker and reddish-brown upon further heating, and boils at 444°C.
• Used in the match industry, fireworks, rubber production, skin ointments, insecticides, and as a disinfectant.

Compounds of Sulphur:

• Sulphuric Acid (H₂SO₄): Also known as oil of vitriol or the king of chemicals. It is manufactured using the lead chamber or contact process and acts as a strong oxidizing and dehydrating agent. It is used in fertilizer production, explosives, coal tar dyes, drug manufacturing, petroleum refining, and metal surface cleaning.
• Hypo (Sodium Thiosulphate): Primarily used in photography as a fixing agent to remove undecomposed silver halide and as an antichlor to remove excess chlorine in bleaching.

Halogens

The term "halogen" means "salt-former" and includes fluorine, chlorine, bromine, and iodine. These highly reactive elements exist only in combined forms and are known for their strong oxidizing abilities, which decrease from fluorine to iodine.

Chlorine (Cl₂):

• Discovered by Scheele in 1774, chlorine is always found in nature as chlorides like sodium chloride and potassium chloride.
• Produced commercially by electrolysis of brine or molten sodium chloride, it is a yellow-green, pungent, toxic gas.
• Chlorine acts as a bleaching agent in the presence of moisture, forming hypochlorous acid (HClO) that provides bleaching and oxidizing properties.
• Used as a disinfectant, germicide, and bleaching agent in various industries.

Bleaching Powder (Ca(OCl)₂):

• Made by passing chlorine over dry slaked lime powder, it loses its potency over time as chlorine decreases.

Bromine (Br₂):

• Found in sea water and mineral springs as bromides, bromine is a reddish-brown, toxic, heavy liquid.
• It is a weaker bleaching agent compared to chlorine but is used as a germicide, bleaching agent, and in manufacturing ethylene bromide for anti-knock gasoline.

Iodine (I₂):

• Found in sea water as iodides and in certain minerals and seaweeds, iodine is a black, shiny solid that sublimates below its melting point.
• It turns starch solutions blue and is used in goitre treatment and as an antiseptic (tincture of iodine). It is slightly soluble in water and its solubility increases with potassium iodide due to the formation of potassium triiodide.

Noble Gases

Noble gases, including helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn), are characterized by their completely filled valence shells, making them chemically inert and found only in their free states. Radon is not present in the atmosphere.

Uses of Noble Gases:

• Helium: Used in gas-cooled atomic reactors, artificial breathing mixtures for asthma patients, balloons, and as a pressuring agent in rockets.
• Neon: Utilized in neon discharge lamps and advertising signs.
• Xenon: Known as the "stranger gas," it is used in high-intensity photographic flash tubes.
• Krypton: Employed in high-efficiency miner's cap lamps.
• Argon: Commonly used to fill electric bulbs, often mixed with nitrogen.