Metals and Non-Metals: KS3 Chemistry Guide

About 75 per cent of all elements are metals, yet non-metals include some of the most important substances on Earth — oxygen, carbon, nitrogen, and silicon. Knowing how to distinguish metals from non-metals by their properties, and how each group reacts, is fundamental KS3 chemistry, usually studied in Year 8 or Year 9.

Where are metals and non-metals on the periodic table?

The periodic table is divided by a diagonal "staircase" line that runs from boron (B) to astatine (At). Metals sit to the left of this line; non-metals sit to the right. Elements along the staircase (boron, silicon, germanium, arsenic, antimony, tellurium) are called metalloids or semi-metals — they have intermediate properties.

Key groups to know at KS3:

Group | Name | Metal or non-metal? | Examples
Group 1 | Alkali metals | Metal | Lithium, sodium, potassium
Group 2 | Alkaline earth metals | Metal | Magnesium, calcium
Groups 3–12 | Transition metals | Metal | Iron, copper, zinc, nickel
Group 17 | Halogens | Non-metal | Fluorine, chlorine, bromine, iodine
Group 18 | Noble gases | Non-metal | Helium, neon, argon

Carbon, nitrogen, oxygen, phosphorus, and sulfur are also important non-metals found in various groups.

What are the physical properties of metals?

Most metals share a characteristic set of physical properties, although there are exceptions:

Property | Typical metal | Exceptions
State at room temperature | Solid | Mercury (liquid)
Lustre (appearance) | Shiny | —
Malleability | Can be hammered into sheets | —
Ductility | Can be drawn into wires | —
Thermal conductivity | Good conductor of heat | —
Electrical conductivity | Good conductor of electricity | —
Density | Generally high | Lithium, sodium, potassium float on water (very low density)
Melting point | Generally high | Gallium melts in the hand (~30 °C); mercury melts at −39 °C

These properties arise from the metallic bonding structure: metals consist of a lattice of positive metal ions surrounded by a "sea" of delocalised electrons that can move freely, conducting heat and electricity and holding the structure together.

What are the physical properties of non-metals?

Non-metals are more varied in their properties:

Property | Typical non-metal
State at room temperature | Gas or solid (bromine is a liquid)
Lustre | Dull (no metallic shine)
Malleability | Brittle (solid non-metals crack under a hammer)
Thermal conductivity | Poor (good insulators)
Electrical conductivity | Poor (except graphite — a form of carbon)
Density | Generally low

Note for exams: graphite is an exception — it is a non-metal (a form of carbon) that conducts electricity because its layered structure contains delocalised electrons. Diamond, another form of carbon, does not conduct electricity.

How do metals react chemically?

Reaction with oxygen

Most metals react with oxygen in air to form metal oxides. The general word equation is:

metal + oxygen → metal oxide

Example: magnesium burns brightly in air, producing white magnesium oxide:

magnesium + oxygen → magnesium oxide

Metal oxides that dissolve in water form alkaline solutions. For example, calcium oxide reacts with water to form calcium hydroxide solution (limewater), which is alkaline (pH > 7).

Reaction with water

Some metals react with water to produce a metal hydroxide and hydrogen gas:

metal + water → metal hydroxide + hydrogen

The more reactive the metal, the more vigorous this reaction. Sodium reacts vigorously with cold water, fizzing and moving across the surface. Potassium reacts so violently that the hydrogen produced catches fire. Iron, by contrast, only reacts slowly with water over time (rusting), and copper does not react with water at room temperature.

Reaction with dilute acids

Most metals react with dilute hydrochloric or sulfuric acid to form a salt and hydrogen:

metal + acid → salt + hydrogen

For example:

zinc + hydrochloric acid → zinc chloride + hydrogen

The reactivity series

Metals can be arranged in a reactivity series in order of how vigorously they react. From most reactive to least reactive, the key metals at KS3 are:

Potassium > Sodium > Calcium > Magnesium > Aluminium > (Carbon) > Zinc > Iron > (Hydrogen) > Copper > Silver > Gold

Carbon and hydrogen are non-metals included in the series because they can displace metals in some reactions. A more reactive metal will displace a less reactive metal from a solution of its salt — this is a displacement reaction. For example, iron displaces copper from copper sulfate solution because iron is more reactive than copper.

How do non-metals react chemically?

Non-metals react with oxygen to form acidic oxides. For example:

sulfur + oxygen → sulfur dioxide (SO₂)

Sulfur dioxide dissolves in water to form sulfurous acid — one of the gases responsible for acid rain. When non-metal oxides dissolve in water they form acidic solutions (pH < 7), which is the opposite of most metal oxides.

Non-metals do not react with water or dilute acids in the same way metals do. They gain electrons (rather than losing them, as metals do) in chemical reactions.

The Department for Education's Science Programmes of Study for Key Stage 3 requires pupils to understand the properties of metals and non-metals, their positions in the periodic table, the reactivity series, and the reactions of metals with oxygen, water, and acids. BBC Bitesize KS3 Chemistry covers metals, non-metals, the periodic table, and the reactivity series with worked examples and self-test questions.

Frequently asked questions

How can you tell if an element is a metal or a non-metal?

The most reliable test is position on the periodic table — metals are left and centre, non-metals are top-right. Practically, you can test the physical properties: metals are shiny, conduct electricity, and are malleable; non-metals are dull (usually), poor conductors, and brittle if solid. A simple electrical conductivity test using a circuit and a bulb will distinguish most metals (bulb lights) from non-metals (bulb stays off) — with the exception of graphite. Chemical tests also work: metals react with dilute acid to produce hydrogen (bubbles), while non-metals do not react this way.

Why do some metals react more violently than others?

The reactivity of a metal depends on how easily its atoms lose electrons to form positive ions. Metals that lose electrons very easily — such as potassium and sodium — are highly reactive because they readily give electrons to other substances (water, oxygen, acid). Metals that hold onto their electrons more tightly — such as copper, silver, and gold — are much less reactive. This is why gold does not tarnish or rust: it does not readily react with oxygen or water in everyday conditions. The reactivity series is a way of ranking metals by how easily they lose electrons.

What is a displacement reaction and how does it work?

A displacement reaction occurs when a more reactive metal takes the place of a less reactive metal in a compound. For example, if you add iron filings to blue copper sulfate solution, the iron displaces the copper because iron is higher in the reactivity series. The iron atoms lose electrons and become iron ions (Fe²⁺), while the copper ions (Cu²⁺) gain electrons and form solid copper metal — which you can see deposited on the iron. The solution gradually loses its blue colour as copper sulfate becomes iron sulfate. The word equation is: iron + copper sulfate → iron sulfate + copper.

Why is aluminium used for drinks cans if it is quite reactive?

Aluminium sits above zinc in the reactivity series, so at first glance it seems too reactive for everyday use. However, when aluminium is exposed to air it instantly forms a very thin, tough layer of aluminium oxide on its surface. This oxide layer is tightly bonded to the aluminium and is impermeable — it acts as a barrier preventing oxygen and water from reaching the metal underneath. This property, called passivation, makes aluminium very resistant to further corrosion. Aluminium is also low density, strong, and easily shaped, making it ideal for cans, window frames, aircraft, and foil.

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