Carbon has four outer-shell electrons and oxygen has six. Carbon dioxide has formula CO2\mathrm{CO_2}CO2, with carbon between the two oxygen atoms.
Construct a complete outer-shell dot-and-cross diagram for carbon dioxide. Use crosses for carbon's electrons and dots for oxygen's electrons.
Verify your diagram by calculating the total number of outer-shell electrons supplied by the three separate atoms and comparing this with the total shown.
A student draws only one shared pair between carbon and each oxygen, and puts the unused carbon electrons into one lone pair on carbon. Explain why this arrangement does not give carbon a complete outer shell.
53 exam-style questions on Edexcel GCSE Chemistry 2.4 Covalent bonding, covering 2.4.1 Covalent bonding and simple molecules. Each one has a worked solution and a mark scheme showing where the marks go.