1. 1
   Iron (Z = 26) forms both Fe²⁺ and Fe³⁺ ions. Cobalt (Z = 27) forms the complex ion [Co(H₂O)₆]²⁺, which is pink in aqueous solution, and the complex ion [CoCl₄]²⁻, which is blue.

   (a)

   What is the ground-state electron configuration of the Fe³⁺ ion?

   [1 mark]

   • A[Ar]3d³4s²
   • B[Ar]3d⁵
   • C[Ar]3d⁴4s¹
   • D[Ar]3d⁶

   (b)

   What is the oxidation state of cobalt in [CoCl₄]²⁻?

   [1 mark]

   • A−2
   • B+4
   • C+2
   • D+6

   (c)

   Explain why the complex ion [Co(H₂O)₆]²⁺ is coloured.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   The electronegativity values of the period 3 elements are: Na 0.9, Mg 1.3, Al 1.6, Si 1.9, P 2.2, S 2.6 and Cl 3.2. The electronegativity of oxygen is 3.4. A student classifies the oxides Na₂O, MgO, Al₂O₃, SiO₂ and SO₃ by how they behave with acids, bases and water.

   (a)

   Which of the oxides is amphoteric?

   [1 mark]

   • ANa₂O
   • BMgO
   • CSiO₂
   • DAl₂O₃

   (b)

   Which trend across period 3 from sodium to chlorine is correct?

   [1 mark]

   • AElectronegativity increases
   • BAtomic radius increases
   • CMetallic character increases
   • DThe oxides become more basic

   (c)

   Using the electronegativity data, explain why Na₂O is a basic oxide whereas SO₃ is an acidic oxide.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   The first ionisation energies of the period 2 elements, in kJ mol⁻¹, are: Li 520, Be 900, B 801, C 1086, N 1402, O 1314, F 1681 and Ne 2081.

   (a)

   Explain why the first ionisation energy of boron is lower than that of beryllium, and state what this shows about the second main energy level.

   [3 marks]

   (b)

   Explain why the first ionisation energy decreases from nitrogen to oxygen, and discuss how the whole pattern of values from Li to Ne provides evidence for energy sublevels.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Copper(II) ions form the deep-blue complex ion [Cu(NH₃)₄(H₂O)₂]²⁺ with ammonia solution; this complex absorbs light most strongly at a wavelength of 610 nm. Zinc (Z = 30) forms only Zn²⁺ ions, and all of its complexes are colourless. The first eight successive ionisation energies of manganese (Z = 25), in kJ mol⁻¹, are 717, 1509, 3248, 4940, 6990, 9220, 11 500 and 18 770. Manganese forms compounds such as MnSO₄, MnO₂ and KMnO₄, and solid MnO₂ speeds up the decomposition of hydrogen peroxide without being used up. The first four successive ionisation energies of calcium (Z = 20) are 590, 1145, 4912 and 6491 kJ mol⁻¹, and calcium forms only compounds containing Ca²⁺. Use c = 3.00 × 10⁸ m s⁻¹.

   (a)

   Deduce the colour of light absorbed by the copper(II) complex and calculate its frequency. Explain why the copper(II) complex is coloured whereas zinc complexes are colourless.

   [6 marks]

   (b)

   Using the ionisation energy data, explain why manganese shows oxidation states from +2 to +7 whereas calcium shows only +2. Identify one other characteristic property of transition elements shown by manganese in the information given.

   [6 marks]

   Total for question 4: 12 marks

End of questions