The structures of silicon(IV) oxide (each Si bonded to four O atoms in a giant network) and carbon dioxide (O=C=O) are shown. Silicon(IV) oxide has a high melting point whereas carbon dioxide has a very low melting point.

1. aExplain this difference in melting points, referring to the structures of the substances and the bonding between their particles. [3]
2. bDescribe a dot and cross diagram of one silicon atom bonded to four oxygen atoms (draw it on paper; inner shells not needed). [2]

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