Transition elements

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Transition metals
Transition Metals
Coloured Compounds
Diagram 1
Absorption of light energy
Diagram 2
Example: a blue coloured compound arises because:
Experiment – Chromium
Experiment – Manganese
Experiment – Manganese ctd
Experiment – Iron
Experiment – Copper
Experiment – Vanadium (DEMO)
Transition metal colours
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Transition Metals


from Sc to Zn electrons are filling the 3d
orbitals (4s filled already except Cr and
Cu)
A transition element has AT LEAST ONE
ION with a PARTIALLY FILLED d-SHELL
(so Sc, Sc3+ and Zn aren’t – no ion with
partially filled d-shell)
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Coloured Compounds

All 5 d-orbitals in an isolated transition element
have the same energy. When ligands bond to
the central ion, the d-orbitals move up to two
different energy levels. The gap between the
energy levels depends upon – the ligand, the
coordination number and the transition metal
ion.
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Diagram 1
Ligands split
the 3d energy
level
3d orbitals
in a Cu2+
ion
Energy
gap, DE
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Absorption of light energy

An electron can be promoted from the
lower 3d energy level by absorbing energy
EXACTLY equal to the energy gap. This
energy is provided by radiation from the
visible and UV regions of the spectrum.
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Diagram 2
Absorption
of light
energy
Cu(H2O)62+ in
an excited
state
Promotion of electron to
higher energy level
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Example: a blue coloured
compound arises because:
absorption of light energy in the red, yellow, and
green regions of the spectrum. This absorbed
radiation provides the energy for an electron to
be excited to a higher energy level
reflection of blue light only
The colour of a transition metal complex ion
results from the transfer of an electron
between the orbitals of an unfilled d subshell
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Transition metal colours
Zn(II) (ZnSO4) colourless
 Cu(I) (Cu2O) brick red, Cu(II) blue (with
some black compounds), CuI white.
 Mn(VII) (MnO4-) purple, Mn (VI) (MnO42-)
green, Mn(IV) (MnO2) brown, Mn(II) (Mn2+)
colourless/pale pink
 V(V) (VO2+)orange, V(IV) (VO2+) blue,
V(III) (V3+) (green) V(II) (V2+) violet
 Fe(II) pale green, Fe(III) orange

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