(a) The table shows information about some of the elements in the third period. element | Na | Mg | Al | P | S | Cl ---|---|---|---|---|---|--- atomic radius/nm | 0.186 | 0.160 | 0.143 | 0.110 | 0.104 | 0.099 radius of most common ion/nm | 0.095 | 0.065 | 0.050 | 0.212 | 0.184 | 0.181 maximum oxidation number of the element in its compounds | +1 | | | | | +7

1. (a)(i)Complete the table to show the maximum oxidation number of each element in its compounds.[1]
2. (a)(ii)Explain why the atomic radius of elements in the third period decreases from Na to Cl.[3]
3. (a)(iii)The radius of the most common ion of Mg is much smaller than the radius of the most common ion of S. Identify both ions and explain the difference in their radii.[2]
4. (b)(i)Phosphorus is a non-metal in the third period. It reacts vigorously with excess oxygen but slowly with chlorine. Some reactions of phosphorus are shown. [Figure showing reaction scheme: phosphorus + excess O₂(g) (reaction 1) → A(s); phosphorus + Cl₂(g) (reaction 2) → PCl₅(s); PCl₅(s) + water → B(aq) + HCl(aq)] Write an equation to represent reaction 1, the formation of compound A.[1]
5. (b)(ii)Give two observations you could make in reaction 2.[2]
6. (b)(iii)Name compound B.[1]
7. (c)(i)Cerium is a lanthanoid metal that shows similar chemical reactions to some elements in the third period. Most of cerium's compounds contain Ce³⁺ or Ce⁴⁺ ions. Cerium shows the same structure and bonding as a typical metal. Draw a labelled diagram to show the structure and bonding in cerium.[2]
8. (c)(ii)Cerium(IV) oxide, CeO₂, is a ceramic. Suggest two physical properties of cerium(IV) oxide.[2]
9. (c)(iii)A naturally occurring sample of cerium contains only four isotopes. Data for three of the isotopes are shown in the table. isotope | ¹³⁶Ce | ¹³⁸Ce | ¹⁴⁰Ce | ¹⁴²Ce ---|---|---|---|--- relative isotopic mass | 135.907 | 137.906 | 139.905 | to be calculated percentage abundance | 0.185 | 0.251 | 88.450 | to be calculated The Aᵣ of the sample is 140.116. Use these data to calculate the relative isotopic mass of the fourth isotope in this sample of cerium. Give your answer to three decimal places.[3]

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