Formation of Coloured Ions
Explanation of the origin of colour in transition metal ions due to d-d transitions.
What is Formation of Coloured Ions?
An electronic transition where an electron moves from one d-orbital to another d-orbital within the same atom or ion, typically occurring after the d-orbitals have been split into different energy levels by ligands.
Key points
- Explain the origin of colour in transition metal ions.
- Relate d-d transitions to the absorption and observation of colour.
- Identify factors affecting the colour of transition metal ions.
- Predict whether a given transition metal ion will be coloured or colourless.
Common exam trap
Assuming all transition metal ions are coloured.
Definitions
- Term
d-d Transition
- Meaning
An electronic transition where an electron moves from one d-orbital to another d-orbital within the same atom or ion, typically occurring after the d-orbitals have been split into different energy levels by ligands.
- Term
Ligand
- Meaning
An ion or molecule that binds to a central metal atom to form a coordination complex.
- Term
Complementary Colour
- Meaning
The colour perceived when a substance absorbs certain wavelengths of light; it is the colour that is opposite to the absorbed colour on a colour wheel.
Learning objectives
Explain the origin of colour in transition metal ions.
Relate d-d transitions to the absorption and observation of colour.
Identify factors affecting the colour of transition metal ions.
Predict whether a given transition metal ion will be coloured or colourless.
Prerequisites
Electronic configuration of transition elements
Concept of d-orbitals
Visible spectrum of light
Basic understanding of chemical bonding and ligands
Common mistakes
Assuming all transition metal ions are coloured.
Confusing the absorbed colour with the observed colour.
Not considering the role of ligands in splitting d-orbitals.
Forgetting that completely filled or empty d-orbitals result in colourless ions.
Keywords
Transition elements
Coloured ions
d-d transitions
Ligand field theory
Crystal field splitting
Visible spectrum
Complementary colours
Oxidation state
Practice preview
What is the primary reason for the colour of transition metal ions in aqueous solutions?…
easy
Why are Cu+ ions typically colourless, while Cu2+ ions are coloured?…
medium
Which of the following elements typically forms coloured ions in its common oxidation states?…
easy