What Are Non-Metals?

Non-metals are elements that generally lack the physical and chemical properties of metals. They are mostly found on the right side of the periodic table.

Non-metals play an important role in many chemical compounds and biological systems.

Examples of common non-metals include:

• Oxygen (O)
• Carbon (C)
• Nitrogen (N)
• Sulfur (S)
• Chlorine (Cl)

These elements are essential in living organisms, industrial chemicals, and environmental processes.

Physical Properties of Non-Metals

Non-metals have several physical properties that distinguish them from metals.

Poor Conductors of Electricity

Most non-metals are poor conductors of electricity.

This is because they do not have free-moving electrons like metals.

Example:

Sulfur does not conduct electricity.

(An exception is graphite, a form of carbon, which can conduct electricity.)

Poor Conductors of Heat

Non-metals generally do not conduct heat well.

They are often used as insulators.

Example:

Plastic materials (made from non-metal compounds) are used to insulate electrical wires.

Low Melting and Boiling Points

Many non-metals have low melting and boiling points.

Because of this, many non-metals exist as gases or liquids at room temperature.

Examples:

• Oxygen – gas
• Nitrogen – gas
• Bromine – liquid

Brittle Solids

Solid non-metals are usually brittle, meaning they break easily when hammered.

This is very different from metals, which are malleable.

Example:

Solid sulfur is brittle and breaks easily.

Chemical Properties of Non-Metals

Non-metals also have characteristic chemical properties.

Gain Electrons in Reactions

Non-metals tend to gain electrons during chemical reactions.

This means they form negative ions (anions).

Example:

Cl + e⁻ → Cl⁻

Chlorine gains an electron to form a chloride ion.

Form Covalent Bonds

Non-metals commonly form covalent bonds by sharing electrons with other atoms.

Example:

Water molecule (H₂O) forms through covalent bonding between hydrogen and oxygen.

React with Metals

Non-metals often react with metals to form ionic compounds.

Example:

Sodium reacts with chlorine to form sodium chloride.

2Na + Cl₂ → 2NaCl

Comparison Between Metals and Non-Metals

PropertyMetalsNon-MetalsElectrical conductivityGood conductorsPoor conductorsHeat conductivityGood conductorsPoor conductorsMalleabilityMalleableBrittleElectron behaviourLose electronsGain electronsBonding typeMetallic / ionicCovalent

This comparison helps students understand how elements behave in chemical reactions.

Importance of Non-Metals

Non-metals are essential in many areas such as:

• Biological systems (oxygen and carbon in living organisms)
• Chemical manufacturing
• Water treatment and environmental chemistry
• Fertiliser production

Many important molecules in life, such as proteins, DNA, and carbohydrates, contain non-metal elements.

Exam Tip (5070)

Students are often asked to:

• Describe physical properties of non-metals
• Compare metals and non-metals
• Explain how non-metals gain electrons in reactions

Example exam question:

Why are non-metals poor conductors of electricity?

Answer:

Non-metals do not contain free-moving electrons, so electricity cannot flow through them easily.

Practice Question

Which type of ions do non-metals usually form?

Answer

Non-metals usually form negative ions (anions).

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