4.2.3—The type of structure and bonding present

Start by recording the conditions of the evidence: melting or boiling behaviour, electrical conductivity in the stated state, solubility in water, hardness or malleability, and any physical state. Do not compare a solid conductivity result with a molten or aqueous result as if they were the same test.

Use the evidence to narrow the structure: high melting behaviour suggests strong attractions or an extended network; mobile charge in a solid supports a metallic structure, while mobile charge only when molten or in solution supports an ionic structure. Low melting behaviour and weak conductivity support a simple molecular structure, subject to polarity and hydrogen-bonding exceptions.

Check the remaining observations against the candidate. Distinguish giant covalent materials from simple molecular substances using the extent of covalent bonding and the resulting melting behaviour; use graphite’s delocalised electrons and layered softness, and diamond or silicon(IV) oxide’s hard network, as source-supported contrasts.

State the best-supported structure and the linked causal evidence: particle type and bonding/attraction → mobility or energy needed → observed properties. A single property is rarely decisive; if evidence is incomplete or an exception applies, state the limitation rather than forcing a classification.

Do not identify a structure from melting point alone, call every high-melting substance ionic, or treat insolubility as proof of one structure. Keep the deduction on the four syllabus structure classes and their source-supported property signatures; detailed reaction or energetics analysis belongs elsewhere.