In a water molecule, H2O\mathrm{H_{2}O}H2O, the oxygen atom has eight electrons in its outer shell, although an oxygen atom has only six outer electrons.
Which statement explains why the water molecule has no overall charge?
Oxygen gains two electrons from the hydrogen atoms, and these charges then cancel
Shared electrons count in both outer shells, so no electrons are gained or lost
The two extra electrons are balanced by two extra neutrons in the oxygen nucleus
Oxygen gains two electrons and loses two protons, so the two changes cancel out
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.