CHEMISTRY · Stage 7 · Chapter 3: Metals and Non-Metals

Chemistry 3.5 Explaining metal and non-metal properties

5 min read 7 parts Lesson 5 of 7

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Lesson summary

3.5 Explaining metal and non-metal properties — Alhussan International Academy — Chemistry (Stages 7–9) notes: Explain the physical properties of metals and non-metals in terms of how their particles are arranged and held together.PropertyMetalsNon-metalsAppearanceShinyDull when …

Delocalised electrons
Metallic bonding
High melting points
Conductivity
Malleable and ductile
Low melting points

Part 1 of 7Typical properties

Property	Metals	Non-metals
Appearance	Shiny	Dull when solid
State at 20 °C	Mostly solid (mercury is liquid)	Many are gases
Conductivity	Good	Poor (graphite is an exception)
Shaping	Malleable and ductile	Brittle
Melting and boiling points	High	Mostly low
Strength	Strong	Weak when solid
Sound	Sonorous	Not sonorous

Method — consider how the particles are arranged and how strongly they are held together.

Part 2 of 7Metallic bonding

Structurein a metal the atoms are packed closely in regular layers.
Delocalised electronsthe outer electrons are not held to one atom but move freely throughout the structure.
Metallic bonding the attraction between positive metal ions and the sea of delocalised electrons.

Part 3 of 7Explaining metal properties

High melting points — the atoms or ions are held together strongly, so much energy is needed to overcome the attraction.
- Most metals are therefore solid at 20 °C.
Strength — the particles are held together strongly, especially when mixed with other elements in alloys.
Conductivity — the free electrons carry electric charge and pass on energy rapidly when heated.
Malleable and ductile — layers of atoms can slide over each other without breaking the bonding, because the electrons keep holding the structure together.

Part 4 of 7Explaining non-metal properties

1Low melting points2 points

— most non-metals exist as single atoms or molecules that are attracted to each other only weakly.

Helium, neon, argon and krypton exist as single atoms.
An oxygen molecule has two atoms held tightly together, but the molecules are attracted to one another only weakly.

2Small molecules2 points

— most non-metals such as O₂ and S₈ have strong covalent bonds inside the molecule but weak forces between molecules.

Little energy is needed to separate the molecules, so many are gases.
Low melting points are explained by weak forces between molecules, not weak bonds inside molecules.

3No conduction

— there are no free electrons, so non-metals do not conduct electricity.

4Brittleness2 points

— iodine exists as two-atom molecules arranged in a pattern in the crystal.

Molecules are attracted weakly, so a dropped crystal breaks between one row of molecules and another.
The pieces have straight edges.

Part 5 of 7Giant non-metal structures

Diamond — every carbon atom is bonded to four others in a rigid network, so it is extremely hard with a very high melting point but does not conduct.
Graphite — carbon atoms form layers in which each atom has a spare electron that can move along the layer.
- It conducts electricity.
- The layers slide easily, so it is soft and used in pencils.

Part 6 of 7Choosing materials

Metals suit cables, pans and structures.
- Copper is used for wires because free electrons conduct electricity and it is ductile.
Non-metals — plastics, made largely from carbon compounds, suit insulation.
Exceptions — silicon is a shiny solid and a semiconductor, and mercury is a liquid metal, which shows that classification is a model.

Part 7 of 7Link to the periodic table

Boundary — a stepped line separates metals from non-metals.
Metalloids — elements next to the line, such as silicon and germanium, look metallic but behave in between.
- Silicon is a semiconductor, used in microchips and solar cells.
Oxides — metal oxides are usually basic and non-metal oxides acidic.

Last updated: 13 October 2026