Metals & Non-Metals

Definition and Classification

Elements in the periodic table are broadly classified as metals or non-metals based on their physical and chemical properties.

Metals

• Usually found on the left and centre of the periodic table.
• Have characteristic physical properties such as being shiny, malleable, and good conductors.
• Chemically, metals tend to lose electrons during reactions to form positive ions (cations).

Non-Metals

• Located on the right side of the periodic table (excluding the noble gases).
• Have physical properties different from metals, such as being dull and brittle if solid.
• Chemically, non-metals tend to gain electrons to form negative ions (anions) or share electrons in reactions.

Physical differences between metals and non-metals include appearance, state, and conductivity. Chemical differences relate to how they react and form ions.

Physical Properties of Metals

• Malleable and ductile: Metals can be hammered into sheets (malleable) or drawn into wires (ductile) without breaking.
• Good conductors of heat and electricity: Metals allow heat and electric current to pass through easily due to free electrons.
• High melting and boiling points: Most metals have high melting and boiling points, meaning they are solid at room temperature (except mercury).

For example, copper is a metal that is malleable and an excellent conductor of electricity, which is why it is used in electrical wiring.

Physical Properties of Non-Metals

• Brittle if solid: Non-metals break or shatter when hammered rather than bending.
• Poor conductors of heat and electricity: Most non-metals do not conduct electricity or heat well (exceptions include graphite, an allotrope of carbon that conducts electricity due to its structure).
• Lower melting and boiling points: Many non-metals have relatively low melting and boiling points and can be gases or solids at room temperature.

For instance, sulfur is a non-metal that is brittle and a poor conductor of electricity.

Chemical Properties

The chemical behaviour of metals and non-metals differs mainly in how they gain or lose electrons during reactions:

• Metals tend to lose electrons to form positive ions (cations). For example, sodium (a metal) loses one electron to form Na⁺.
• Non-metals tend to gain electrons to form negative ions (anions) or share electrons in covalent bonds. For example, chlorine (a non-metal) gains one electron to form Cl⁻.

This difference in electron transfer explains why metals and non-metals often react together to form ionic compounds.

Reactivity trends overview: Metals generally become less reactive across a period (left to right) and more reactive down a group, while non-metals show the opposite trend. However, detailed trends for specific groups like alkali metals or halogens are covered in other topics.

Example:

Sodium (a metal) reacts with chlorine (a non-metal) to form sodium chloride (table salt). Sodium loses one electron to become Na⁺, and chlorine gains one electron to become Cl⁻. These oppositely charged ions attract, forming an ionic bond.