ASRJC 2025 H2 Chem Transition Elements Notes

©2025ASRJC/CHEM 1 ANDERSON SERANGOON JUNIOR COLLEGE 2025 JC2 H2 Chemistry AN INTRODUCTION TO THE CHEMISTRY OF TRANSITION ELEMENTS Content • General physical and characteristic chemical properties of the first set of transition elements, titanium to copper • Colour of complexes Learning Outcomes Candidates should be able to: (a) explain what is meant by a transition element, in terms of d block elements forming one or more stable ions with partially filled d subshells (b) state the electronic configuration of a first row transition element and its ions (c) explain why atomic radii and first ionisation energies of the transition elements are relatively invariant (d) contrast, qualitatively, the melting point and density of the transition elements with those of calcium as a typical s block element (e) describe the tendency of transition elements to have variable oxidation states (f) predict from a given electronic configuration, the likely oxidation states of a transition element (g) describe and explain the use of Fe3+/Fe2+, MnO 4–/Mn2+ and Cr 2O72–/Cr3+ as examples of redox systems (h) predict, using E values, the likelihood of redox reactions (i) define the terms ligand and complex as exemplified by the complexes of copper(II) ions with water, ammonia and chloride ions as ligands (including the transition metal complexes found in the Qualitative Analysis Notes) (j) explain qualitatively that ligand exchange may occur, as exemplified by the formation of the complexes in (i), including the colour changes involved, and CO/O2 in haemoglobin (k) describe, using the shape and orientation of the d orbitals, the splitting of degenerate d orbitals into two energy levels in octahedral complexes (l) explain, in terms of d orbital splitting and d-d transition, why transition element complexes are usually coloured [knowledge of the relative order of ligand field strength is not required] (m) explain how some transition elements and/or their compounds can act as catalysts (see also 8(j)) References 1. Chemistry for Advanced Level, Peter Cann and Peter Hughes 2. Understanding Advanced Physical Inorganic Chemistry, The Learner’s Approach, Jeanne Tan and Chan Kim Seng.

©2025ASRJC/CHEM 2 1. INTRODUCTION In the Periodic Table, the d block elements are found in groups 3 to 12. A transition element is a d block element that can form one or more stable ions with _______________ d subshells. The ten elements from scandium (Sc) to zinc (Zn) comprise the 3d block of elements. Based on the definition in our syllabus, we will focus on the following eight elements. Ti V Cr Mn Fe Co Ni Cu titanium vanadium chromium manganese iron cobalt nickel copper Sc and Zn are not considered transition elements as they do not form stable ions with partially filled d subshells. Sc [Ar] 3d1 4s2 Zn [Ar] 3d10 4s2 Sc3+ [Ar] Zn2+ [Ar] 3d10 The common stable ion for Sc is Sc3+, which has an e