An aerospace engineer is evaluating materials for a high-temperature electrical sensor. They are comparing the electrical properties of solid potassium bromide (KBr\text{KBr}KBr) and solid nickel (Ni\text{Ni}Ni).
Explain, in terms of structure and bonding, why solid potassium bromide is an electrical insulator, whereas solid nickel is an electrical conductor.
59 exam-style questions on Edexcel GCSE Chemistry 2.5 Types of substance, covering 2.5.1 Classifying substances by structure and bonding, 2.5.2 Properties of ionic and simple molecular substances, 2.5.3 Giant covalent structures: diamond and graphite, 2.5.4 Fullerenes, graphene and simple polymers, 2.5.5 Properties of metals and non-metals, and 2.5.6 Limitations of bonding models and representations. Each one has a worked solution and a mark scheme showing where the marks go.