O-LevelChemistryAtomic Structure5070/21 · Oct/Nov 2021 · Q1010 Marks

This question is about elements in Group IV of the Periodic Table. (a) The table shows some properties of the Group IV elements. element | density at room temperature in g/cm³ | melting point in °C | boiling point in °C carbon (diamond) | | 3550 | 4827 silicon | 2.34 | 1410 | 2355 germanium | 5.35 | 937 | 2830 tin | | 232 | 2260 lead | 11.34 | 328 | 1740 [Figure 10.1]

(a)(i)Predict the density of tin.[1]
(a)(ii)Describe the general trend in the boiling points of the Group IV elements.[1]
(a)(iii)Predict the state of silicon at 1600°C. Give a reason for your answer.[1]
(b)(i)The structure of two compounds of silicon, P and Q, are shown. [Figure 10.2] oxygen atom (legend) silicon atom (legend) chlorine atom (legend) Explain in terms of structure and bonding why compound P has a high melting point and compound Q has a low melting point. compound P compound Q[4]
(b)(ii)Draw a dot-and-cross diagram for a molecule of compound Q. Show only the outer shell electrons.[1]
(c)A compound of carbon, hydrogen and silicon has the formula Si(CH₃)₄ Calculate the percentage by mass of carbon in this compound.[2]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.

[1] 10(a)(i) values between 5.40 and 11.00 (inclusive of these values)
[1] 10(a)(ii) decrease down the group / increase up the group
[1] 10(a)(iii) liquid AND 1600 (°C) is lower than the boiling point AND 1600 (°C) is higher than the melting point
[1] 10(b)(i) P is a giant covalent structure / giant covalent lattice
[1] 10(b)(i) P (all) bonds (throughout lattice) are strong (if covalent or bonds between atoms already mentioned)
[1] 10(b)(i) Q is a simple molecular structure / small molecules / simple molecule
[1] 10(b)(i) Q weak forces between molecules
[1] 10(b)(ii) 4 pairs of bonding electrons between each Cl and Si AND 6 unpaired electrons on each chlorine
[1] 10(c) (molar mass of Si(CH3)4) = 88
[1] 10(c) 54.5(%)

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