1. 1
   Chromium (Z = 24) is used to plate car parts, manganese (Z = 25) compounds are used in batteries, and copper(I) oxide (containing Cu⁺ ions; Cu has Z = 29) is used in anti-fouling paint for ships.

   (a)

   What is the ground-state electron configuration of the Cu⁺ ion?

   [1 mark]

   • A[Ar]3d¹⁰
   • B[Ar]4s¹3d⁹
   • C[Ar]4s²3d⁸
   • D[Ar]4s¹3d¹⁰

   (b)

   Which species has the same number of unpaired electrons as a ground-state chromium atom?

   [1 mark]

   • AMn²⁺
   • BFe
   • CV
   • DMn⁺

   (c)

   Deduce the number of unpaired electrons in a chromium atom and explain why its configuration is not [Ar]4s²3d⁴.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In the emission spectrum of hydrogen, the series of lines in the ultraviolet region converges to a limit at a wavelength of 91.2 nm. Use c = 3.00 × 10⁸ m s⁻¹, h = 6.63 × 10⁻³⁴ J s and Avogadro's constant = 6.02 × 10²³ mol⁻¹.

   (a)

   Which electron transition corresponds to the convergence limit of this series?

   [1 mark]

   • An = 2 → n = 1
   • Bn = ∞ → n = 1
   • Cn = ∞ → n = 2
   • Dn = ∞ → n = 3

   (b)

   What is the frequency of radiation at the convergence limit?

   [1 mark]

   • A3.29 × 10⁶ Hz
   • B3.04 × 10⁻¹⁶ Hz
   • C3.29 × 10¹⁵ Hz
   • D2.18 × 10⁻¹⁸ Hz

   (c)

   Calculate the first ionisation energy of hydrogen in kJ mol⁻¹.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   The first ionisation energies of the period 3 elements, in kJ mol⁻¹, are: sodium 496, magnesium 738, aluminium 578, silicon 787, phosphorus 1012, sulfur 1000, chlorine 1251 and argon 1521.

   (a)

   Explain the general increase in first ionisation energy from sodium to argon.

   [3 marks]

   (b)

   Explain the decreases in first ionisation energy from magnesium to aluminium and from phosphorus to sulfur.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Two unknown elements, X and Y, are both in period 3. The first five successive ionisation energies, in kJ mol⁻¹, are: X: 578, 1817, 2745, 11 577, 14 842. Y: 738, 1451, 7733, 10 543, 13 630. Element Y is in the same group as beryllium and calcium, whose first ionisation energies are 900 and 590 kJ mol⁻¹.

   (a)

   Deduce the group and identity of element X from its successive ionisation energies, and explain the pattern in the data, including why each successive ionisation energy is larger than the previous one.

   [6 marks]

   (b)

   Deduce the group of Y, and use all the data to explain the trend in first ionisation energy down its group and why Y has a higher first ionisation energy than X.

   [6 marks]

   Total for question 4: 12 marks

End of questions