Cobalt, rhodium and iridium are metals in the same group of the Periodic Table.

1. (a)(i)Identify what is meant by [Ar] by giving its full electronic configuration.[1]
2. (a)(ii)The lowest-energy electrons in cobalt are in the 1s orbital. Draw the shape of a 1s orbital.[1]
3. (a)(iii)Deduce the number of unpaired electrons in a cobalt atom.[1]
4. (b)Table 1.1 gives some details of the stable naturally occurring isotopes of rhodium and iridium. Table 1.1 | isotope | number of protons | number of neutrons | total number of electron shells | |:--------|:------------------|:-------------------|:------------------------------| | ¹⁰³Rh ₄₅ | | 58 | | | ¹⁹¹Ir ₇₇ | | | 6 | | ¹⁹³Ir ₇₇ | | | 6 | Complete Table 1.1.[3]
5. (c)(i)Define relative isotopic mass.[2]
6. (c)(ii)Use Table 1.2 to calculate the relative atomic mass, Ar, of iridium in the alloy. Give your answer to two decimal places. Table 1.2 | isotope | relative isotopic mass | relative abundance in alloy | |:--------|:-----------------------|:----------------------------| | ¹⁰³Rh ₄₅ | 102.91 | 50.00 | | ¹⁹¹Ir ₇₇ | 190.96 | 15.18 | | ¹⁹³Ir ₇₇ | 192.96 | 34.82 | relative atomic mass of iridium =[2]
7. (d)(i)Hydrated rhodium(III) chloride contains 20.5% by mass of water of crystallisation. Deduce the integer value of x in RhCl₃•xH₂O. Show your working. x =[2]
8. (d)(ii)Define stereoisomers.[1]
9. (d)(iii)Explain how the conversion of ethene to but-2-ene can be described as an addition reaction.[1]
10. (d)(iv)Draw the two stereoisomers of but-2-ene.[2]

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