Diamond and silicon dioxide (SiO₂) are both giant covalent structures. Which statement correctly explains why both substances have very high melting points?

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Question

Diamond and silicon dioxide (SiO₂) are both giant covalent structures. Which statement correctly explains why both substances have very high melting points?

Accepted Answer

Many strong covalent bonds throughout the structure must be broken to melt the substance — In giant covalent structures, every atom is covalently bonded to its neighbours throughout the entire lattice. A very large number of strong covalent bonds must be broken to melt the substance, requiring a very large amount of energy. Option B confuses molecular mass with bond strength. Option C incorrectly refers to intermolecular forces, which apply to simple molecules, not giant covalent structures. Option D describes metallic bonding, not covalent bonding.

Answer

Large molecules with high relative molecular masses require more energy to move

Answer

Strong intermolecular forces between layers must be overcome to melt the substance

Answer

Delocalised electrons hold the atoms in fixed positions within the lattice

Answer

Many strong covalent bonds throughout the structure must be broken to melt the substance

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