Explain the differences between metals and non-metals on the basis of…

The idea

Metals and non-metals differ in physical properties like conductivity and melting point, and in chemical behaviour. Metals have giant structures with delocalised electrons, meaning they conduct electricity, are malleable, and usually have high melting points. Non-metals typically form simple molecules or giant covalent structures; they are often brittle, poor conductors (with exceptions like graphite, which conducts via delocalised electrons), and simple molecular non-metals have lower melting points. Chemically, metals form positive ions by losing electrons. For example, sodium (Group 1) reacts vigorously with water. Non-metals gain or share electrons. Chlorine (Group 7) forms negative ions, while Group 0 noble gases are unreactive non-metals with full outer shells.

What earns the marks

• Metals are generally good conductors of electricity because they contain delocalised electrons that are free to move throughout the structure.
• Metals are malleable because layers of positive ions can slide over one another; solid non-metals are often brittle because their atoms are held in fixed covalent lattices or simple molecular structures.
• Metals tend to lose electrons to form positive ions, whereas non-metals tend to gain or share electrons, forming negative ions or covalent bonds.
• Metals usually have high melting points due to strong metallic bonding; many non-metals have lower melting points because they form simple molecular structures with weak intermolecular forces.
• Group 0 noble gases are non-metals with full outer shells, making them unreactive; Group 1 metals are highly reactive because they lose one electron easily.

Common mistakes and how to put them right

• Saying all non-metals are gases.

  Put it right: Many non-metals are solids at room temperature, such as sulfur and carbon, and bromine is a liquid.

• Stating that no non-metals conduct electricity.

  Put it right: Graphite is a form of carbon (a non-metal) that conducts electricity due to delocalised electrons.

• Claiming elemental non-metals have ionic bonds.

  Put it right: Elemental non-metals are bonded covalently or exist as single atoms; ionic bonds only form between metals and non-metals.

Exam tips

• Link each physical property to its structural explanation, for example 'metals conduct electricity because delocalised electrons can move'.
• When comparing, give a paired statement for a metal and a non-metal rather than describing only one side.