General properties of transition metalsAQA A-Level Chemistry: Subtopic test

1. 1
   A student is comparing the electronic structures of some d-block elements. Iron has the configuration [Ar]3d⁶4s², scandium [Ar]3d¹4s², zinc [Ar]3d¹⁰4s² and copper [Ar]3d¹⁰4s¹.

   (a)

   What is the electron configuration of an Fe³⁺ ion?

   [1 mark]

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

   (b)

   Which of these ions is a transition metal ion?

   [1 mark]

   • AZn²⁺
   • BSc³⁺
   • CCa²⁺
   • DCu²⁺

   (c)

   Explain why zinc is not classified as a transition metal even though it is a d-block element.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Cobalt(II) chloride dissolves in water to give the pink complex ion [Co(H₂O)₆]²⁺. Adding excess ammonia solution forms [Co(NH₃)₆]²⁺, and adding concentrated hydrochloric acid forms the blue complex ion [CoCl₄]²⁻.

   (a)

   What is the co-ordination number of cobalt in the complex ion [CoCl₄]²⁻?

   [1 mark]

   • A4
   • B2
   • C6
   • D1

   (b)

   Which statement correctly describes the bonding between a water ligand and the cobalt(II) ion in [Co(H₂O)₆]²⁺?

   [1 mark]

   • AIonic attraction between a water molecule and the Co²⁺ ion
   • BA covalent bond in which cobalt and oxygen each provide one electron
   • CA co-ordinate bond in which a lone pair on oxygen is donated to the Co²⁺ ion
   • DA co-ordinate bond in which a pair of electrons is donated by the Co²⁺ ion to oxygen

   (c)

   Ammonia, NH₃, can act as a ligand but the ammonium ion, NH₄⁺, cannot. Explain why.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Solid iron(II) sulfate dissolves in water to give a pale green solution containing [Fe(H₂O)₆]²⁺. On standing in air the solution slowly turns yellow-brown as iron(III) ions form. Finely divided iron is used as the catalyst in the Haber process.

   (a)

   Identify three characteristic properties of transition metals that are shown by the information, quoting the evidence for each.

   [3 marks]

   (b)

   Iron has the electron configuration [Ar]3d⁶4s². Explain, in terms of its electronic structure, why iron can form both Fe²⁺ and Fe³⁺ ions.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Copper atoms have the configuration [Ar]3d¹⁰4s¹ and zinc atoms [Ar]3d¹⁰4s². Copper(II) sulfate dissolves in water to give a blue solution. Adding excess ammonia solution gives a deep blue solution containing [Cu(NH₃)₄(H₂O)₂]²⁺. Copper(I) chloride is a white solid. Zinc sulfate dissolves to give a colourless solution, and zinc forms only the +2 oxidation state.

   (a)

   Explain why copper is classified as a transition metal but zinc is not, and describe how the properties of copper compounds illustrate characteristic transition metal behaviour.

   [6 marks]

   (b)

   Describe the bonding in the complex ion [Cu(NH₃)₄(H₂O)₂]²⁺, using the terms ligand, complex and co-ordination number, and deduce its co-ordination number.

   [6 marks]

   Total for question 4: 12 marks

End of questions