9701 · 28.1
General physical and chemical properties of the first row of transition elements, titanium to copper — FAQ
Frequently asked questions for 9701 General physical and chemical properties of the first row of transition elements, titanium to copper. Direct answers first, then deeper explanation — then practise with marking.
Why aren't Scandium and Zinc considered transition elements if they are in the d-block?
The definition of a transition element requires the formation of at least one stable ion with a partially filled d-subshell. Scandium's only ion (Sc³⁺) has an empty d-subshell (3d⁰), and Zinc's only ion (Zn²⁺) has a full d-subshell (3d¹⁰). Neither meets the criteria.
Do transition metals have to be in a complex to be coloured?
Yes, essentially. The colour arises from the splitting of d-orbitals, which is caused by the electric field of surrounding ligands in a complex ion. An isolated gaseous metal ion would not be coloured as its d-orbitals would be degenerate (all at the same energy level).
What is the difference between heterogeneous and homogeneous catalysis?
In heterogeneous catalysis, the catalyst is in a different phase from the reactants (e.g., a solid catalyst like iron in the gaseous Haber process). In homogeneous catalysis, the catalyst is in the same phase as the reactants (e.g., aqueous Fe²⁺ ions catalysing a reaction between two other aqueous ions).
Why is the electronic configuration of Copper [Ar] 3d¹⁰ 4s¹ and not [Ar] 3d⁹ 4s²?
The configuration [Ar] 3d¹⁰ 4s¹ is more stable because a completely full d-subshell (3d¹⁰) provides extra stability. The energy difference between 4s and 3d is small enough that it is energetically favourable for an electron to move from the 4s to the 3d subshell to achieve this full d-subshell configuration. A similar exception occurs for Chromium (Cr), which is [Ar] 3d⁵ 4s¹ to achieve a stable half-filled d-subshell.