The newest 20 of 95 written questions. Open one to see it on the real paper.
Complete the electronic configurations of a Co atom and a Co 2+ ion. Co atom: [Ar] Co 2+ ion: [Ar]
See it on the paper →Transition elements have variable oxidation states and form complex ions. State two other typical chemical properties of a transition element.
See it on the paper →Explain why transition elements have variable oxidation states.
See it on the paper →State the type of bonding that exists between H,O and Cr** in [Cr(H,O),]**. doce
See it on the paper →Explain why transition elements form complex ions.
See it on the paper →Suggest a suitable reagent for this conversion. State the type of reaction. FOAQOMM type FEACTION
See it on the paper →[Cr(H,O),(OH),] reacts with an excess of NH,(aq) to form [Cr(NH.),]°*. Complete the equation for this reaction. State the type of reaction. [Cr(H,O)a(OH)a] type FEACTION
See it on the paper →Explain what is meant by bidentate ligand.
See it on the paper →Define transition element.
See it on the paper →Complete the electrons-in-boxes diagram to show the electronic configuration of an isolated gaseous chromium atom. 3d 4s 4p [Ar]
See it on the paper →The 3d orbitals in an isolated Cu 2+ ion are degenerate. Complete the diagram to show the relative energies of the 3d orbitals in an isolated Cu 2+ ion and in Cu 2+ in a tetrahedral complex. energy isolated Cu 2+ ion Cu 2+ in a tetrahedral complex
See it on the paper →Complete Table 2.1 to show the formula and colour of each of the cobalt-containing species present in A, B and C. Identify the type of reaction forming each of B and C. Table 2.1 formula of cobalt-containing species colour of cobalt-containing species type of reaction A B C
See it on the paper →Suggest a suitable reagent for the formation of [CoCl 4 ] 2– from solution A.
See it on the paper →Complete Fig. 2.2 to show the relative energies of the 3d orbitals in an isolated Co 2+ ion and in Co 2+ in a tetrahedral complex. energy isolated Co 2+ ion Co 2+ in a tetrahedral complex
See it on the paper →Explain why transition elements have variable oxidation states.
See it on the paper →Silver can form compounds containing either Ag + or Ag 2+ ions. Explain why silver is a transition element.
See it on the paper →Define complex.
See it on the paper →Complete Table 3.1. Table 3.1 complex ion ligand coordination number E Fe 2+ NH 3 6 formula and charge of complex [FeCl 4 ] 2– F G [Fe(en) 3 ] 3+ en Table 3.1 gives some details of different complexes of Fe 2+ and of Fe 3+ . (ii)
See it on the paper →U can act as a bidentate ligand. Explain what is meant by a bidentate ligand.
See it on the paper →The d-orbitals of the Co 2+ ions present in complex ion G are split. State the number of d-orbitals that are at a higher energy level and the number of d-orbitals that are at a lower energy level in each Co 2+ ion. number of d-orbitals at a higher energy level number of d-orbitals at a lower energy level
See it on the paper →Comprehensive responses • Most candidates defined transition element accurately. Limited responses • Some candidates did not include the word ‘stable’ when describing the ions that transition elements form. • Other answers omitted d when referring to incomplete orbitals.
— Examiner report, February/March 2026, 9701/42 Q1(a)(i) (Cambridge)
Comprehensive responses • Many candidates correctly completed the electrons-in-boxes diagram. Each of the five dorbital boxes and the 4s box should contain a single arrow. Limited responses • Nearly all candidates realised that they needed to draw six electrons in the boxes. Many candidates still put two electrons in the 4s box.
— Examiner report, February/March 2026, 9701/42 Q1(a)(ii) (Cambridge)
This was not well known. Candidates were required to state that silver can form stable ions with incomplete d orbitals. A common error was stating silver has partially filled d-orbitals and forms stable ions.
— Examiner report, February/March 2025, 9701/42 Q1(a) (Cambridge)
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