Poly(ethene) is used to make plastic bags. Its structure can be written as [ −CH2−CH2− ]n\left[\!-\text{CH}_2-\text{CH}_2-\!\right]_n[−CH2−CH2−]n. When the repeating unit is drawn, the bond lines at each end of the unit are drawn passing through the square brackets.
What do the bond lines passing through the brackets show?
A hydrogen atom is bonded to each end of the chain
Each repeating unit is joined to the next by a double bond
The structure is a giant covalent network, not a molecule
The chain continues beyond the repeating unit on both sides
98 exam-style questions on AQA GCSE Chemistry 2.1 Chemical bonds, ionic, covalent and metallic, covering 2.1.1 Chemical bonds, 2.1.2 Ionic bonding, 2.1.3 Ionic compounds, 2.1.4 Covalent bonding, and 2.1.5 Metallic bonding. Each one has a worked solution and a mark scheme showing where the marks go.