Describe the bonding and structure of SiO2 and explain how this affects its melting point.

SiO2 has a giant covalent structure where each silicon atom is covalently bonded to four oxygen atoms in a tetrahedral arrangement. This strong covalent bonding throughout the structure results in a high melting point of approximately 1710 °C. This answer is anchored to Period 3 oxides (A-level only).

SiO2 has a giant covalent structure where each silicon atom is covalently bonded to four oxygen atoms in a tetrahedral arrangement. This strong covalent bonding throughout the structure results in a high melting point of approximately 1710 °C. is the best answer because it directly supports the AQA A-Level Chemistry objective to explain melting point trends of Period 3 oxides. This reasoning is anchored to Period 3 oxides (A-level only) in Properties of Period 3 elements and their oxides (A-level only), and it separates Period 3 oxide from similar A-Level ideas rather than relying on a vague recall statement. Other options are weaker if they use the wrong evidence, calculation, mechanism, observation, unit, or conclusion for this subtopic.