Transition elements
Transition elements
- A transition element is a d-block element that forms one or more stable ions with incomplete d orbitals.
- Scandium and zinc are d-block but not transition (their stable ions have empty or full d orbitals).
- Transition metals share four special properties.
Practice
A transition element is a d-block element that:
The incomplete d orbitals (in a stable ion) define a transition element.
Practice
Why are scandium and zinc not classed as transition elements?
Sc³⁺ has an empty d sub-shell and Zn²⁺ a full one, so neither has incomplete d orbitals in its stable ion.
Four key properties (and why)
| Property | Reason |
|---|---|
| variable oxidation state | the 3d and 4s sub-shells are close in energy |
| act as a catalyst | more than one oxidation state, plus vacant d orbitals |
| form complex ions | vacant d orbitals accept lone pairs |
| form coloured compounds | electrons move between split d orbitals |
Practice
Transition metals show variable oxidation states because:
Similar energies mean similar small amounts of energy can remove different numbers of electrons.
Practice
Transition metal compounds are coloured because:
Ligands split the d orbitals; absorbing light of the gap energy gives the colour we see.
You've got it
Key idea
- a transition element forms stable ions with incomplete d orbitals (not Sc or Zn)
- four properties: variable oxidation state (3d/4s close), catalysis, complex ions (accept lone pairs), colour (split d orbitals)