The mass spectrum of silicon is shown. [Diagram: A mass spectrum showing relative intensity on the y-axis (up to 1.0) and m/e on the x-axis (from 28 to 30). Peaks are at m/e 28 (relative intensity 0.922), m/e 29 (relative intensity 0.047), and m/e 30 (relative intensity 0.031).]

1. (a)(i)Calculate the Ar of silicon. Give your answer to two decimal places.[1]
2. (a)(ii)Silicon forms a low boiling point chloride which reacts with water. Write an equation to show the reaction of the chloride with water.[1]
3. (a)(iii)Draw a three-dimensional diagram showing the shape of the chloride. Give the Cl-Si-Cl bond angle.[2]
4. (a)(iv)Silicon reacts with oxygen to form a high melting point oxide. • Suggest the formula of the oxide. • Suggest, in terms of structure, why the oxide has a high melting point whereas the chloride has a low boiling point.[2]
5. (b)(i)Element A is in the same period as silicon. Element A reacts with dilute nitric acid to form a nitrate. This nitrate decomposes on heating to form an oxide. Write an equation for the decomposition of the nitrate.[2]
6. (b)(ii)The oxide of element A has a high melting point. Suggest the structure and bonding present in the oxide of A.[1]

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