A ball and stick model of part of a sodium chloride lattice contains 14 sodium ions and 13 chloride ions.
A student says that the model shows that the formula of sodium chloride is Na14Cl13\mathrm{Na_{14}Cl_{13}}Na14Cl13.
Which statement explains why the student is wrong?
Sodium chloride is made of separate NaCl\mathrm{NaCl}NaCl molecules, so the formula is always NaCl\mathrm{NaCl}NaCl.
The model shows only a small part of the giant lattice. In the whole lattice there is one sodium ion for every chloride ion.
The sticks represent extra electrons, so they must be included in the formula.
The model does not show the ions to scale, so the numbers of ions in it cannot be counted.
64 exam-style questions on OCR GCSE Chemistry 2.2 Bonding, covering 2.2.1 Metals, non-metals and the Periodic Table, 2.2.2 Types of chemical bonding and dot and cross diagrams, 2.2.3 Limitations of bonding models, and 2.2.4 Reactivity, atomic number and the modern Periodic Table. Each one has a worked solution and a mark scheme showing where the marks go.