Chapter 3: Metals and Non-metals

3.1 Physical Properties

Metallic Lustre: Metals, in their pure state, have a shining surface.
Hardness: Metals are generally hard, but the hardness varies from metal to metal. Alkali metals like sodium, potassium, and lithium are so soft they can be cut with a knife.
Malleability: The property by which some metals can be beaten into thin sheets. Gold and silver are the most malleable metals.
Ductility: The ability of metals to be drawn into thin wires. Gold is the most ductile metal.
Conductivity: Metals are good conductors of heat and have high melting points. Silver and copper are the best conductors of heat, whereas lead and mercury are comparatively poor. Metals are also good conductors of electricity, which is why electrical wires are coated with polyvinylchloride (PVC) or rubber-like materials.
Sonorous: The property of metals to produce a ringing sound when they strike a hard surface.

Physical State: Non-metals are either solids or gases at room temperature, except bromine which is a liquid.
Lustre Exception: Non-metals are generally non-lustrous, but iodine is a non-metal that is lustrous.
Allotropes: Carbon is a non-metal that exists in different forms called allotropes. Diamond (an allotrope of carbon) is the hardest natural substance known and has a very high melting/boiling point. Graphite is an allotrope of carbon that conducts electricity.
Oxide Nature: Most non-metals produce acidic oxides when dissolved in water, while most metals give rise to basic oxides.

3.2 Chemical Properties of Metals

Metal Oxides: Almost all metals combine with oxygen to form metal oxides, which are generally basic. For example, copper heated in air forms black copper(II) oxide.
Amphoteric Oxides: Metal oxides which react with both acids as well as bases to produce salts and water (e.g., aluminium oxide and zinc oxide).
Anodising: A process of forming a thick, protective oxide layer of aluminium using electrolysis to improve its corrosion resistance.
Reactivity with Oxygen: Highly reactive metals like sodium and potassium react vigorously and are stored under keresone oil to prevent accidental fires.

Metal Hydroxide Formation: Metals react with water to produce metal oxides/hydroxides and hydrogen gas.
Cold Water Reactions: Sodium and potassium react violently and exothermically with cold water, causing the evolved hydrogen to catch fire. Calcium reacts less violently, and the metal starts floating as hydrogen bubbles stick to its surface.
Hot Water & Steam Reactions: Magnesium reacts with hot water. Metals like aluminium, iron, and zinc react only with steam to form oxides, while lead, copper, silver, and gold do not react with water at all.

Hydrogen Gas Evolution: Metals react with dilute acids to produce a salt and hydrogen gas.
Nitric Acid Exception: Hydrogen gas is not evolved when a metal reacts with nitric acid (HNO₃) because it is a strong oxidising agent, except in reactions with magnesium and manganese.
Aqua Regia: A highly corrosive, fuming liquid made of a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in a 3:1 ratio, capable of dissolving gold and platinum.

Displacement Reaction: A reaction where a highly reactive metal displaces a less reactive metal from its salt solution (Metal A + Salt solution of B → Salt solution of A + Metal B).
Reactivity Series: A list of metals arranged in the order of their decreasing activities, ranging from highly reactive potassium and sodium down to least reactive gold and silver.

3.3 How do Metals and Non-metals React?

Ionic Compounds: Also known as electrovalent compounds, these are formed by the transfer of electrons from a metal to a non-metal, held together by strong electrostatic forces.
Physical Nature: Solid, hard, and generally brittle substances.
Melting and Boiling Points: Very high, because a considerable amount of energy is required to break the strong inter-ionic attraction.
Solubility: Soluble in water but insoluble in organic solvents like kerosene and petrol.
Electrical Conduction: Ionic compounds conduct electricity in the molten state or in solution because ions are free to move, but they do not conduct in the solid state due to their rigid structure.

3.4 Occurrence of Metals

Minerals: Naturally occurring elements or compounds in the earth's crust.
Ores: Minerals that contain a very high percentage of a particular metal which can be profitably extracted.
Gangue: The large amounts of impurities (like soil and sand) contaminating ores mined from the earth.
Low Reactivity Extraction: Metals at the bottom of the activity series are very unreactive and can often be reduced to metals by heating their oxides alone (e.g., heating cinnabar, HgS, to extract mercury).

Roasting: The process of converting sulphide ores into oxides by heating them strongly in the presence of excess air.
Calcination: The process of converting carbonate ores into oxides by heating them strongly in limited air.
Reduction: Metal oxides are reduced to metallic form using reducing agents like carbon (coke) or highly reactive metals like aluminium.
Thermit Reaction: A highly exothermic displacement reaction where iron(III) oxide reacts with aluminium to produce molten iron, used to join railway tracks.

Electrolytic Reduction: Highly reactive metals (like sodium, magnesium, and calcium) cannot be reduced by carbon and must be obtained by the electrolysis of their molten chlorides.
Electrolytic Refining: The process of purifying crude metals using electricity. The impure metal is made the anode, a thin strip of pure metal is the cathode, and the metal salt is the electrolyte.
Anode Mud: The insoluble impurities that settle down at the bottom of the anode during electrolytic refining.

3.5 Corrosion

Corrosion: The slow degradation of metal surfaces when exposed to air, moisture, and chemicals (e.g., green basic copper carbonate coating on copper, or rust on iron).
Galvanisation: A method of protecting steel and iron from rusting by coating them with a thin protective layer of zinc.
Alloying: A method of improving metal properties by preparing a homogeneous mixture of two or more metals, or a metal and a non-metal (e.g., stainless steel, brass, bronze).
Amalgam: An alloy in which one of the constituent metals is mercury.