Transition Metals (2018 - 04 - 16 01 - 41 - 52 UTC)

TRANSITION METALS
The elements in the Periodic Table which correspond to

the d levels filling are called d block elements. The first
row of these is shown in the shortened form of the
Periodic Table below.
The electronic structures of the d block elements
shown are:
Sc [Ar] 3d14s2
Ti [Ar] 3d24s2
V [Ar] 3d34s2
Cr [Ar] 3d54s1
Mn [Ar] 3d54s2
Fe [Ar] 3d64s2
Co [Ar] 3d74s2
Ni [Ar] 3d84s2
Cu [Ar] 3d104s1
Zn [Ar] 3d104s2
PROPERTIES OF THE FIRST ROW
TRANSITION ELEMENTS.
Page #237
ATOMIC RADIUS,IONIZATION
ENERGY AND MELTING AND
BOILING POINTS.
Page #238
A TRANSITION
METAL IS ONE WHICH
FORMS ONE OR
MORE STABLE IONS
WHICH HAVE
INCOMPLETELY
FILLED d ORBITALS
When d-block elements form ions, the
4s electrons are lost first.
To write the electronic structure for Co2+:
Co [Ar] 3d74s2
Co2+ [Ar] 3d7
The 2+ ion is formed by the loss of the two 4s electrons.

EXAMPLES OF VARIABLE OXIDATION STATES IN
THE TRANSITION METALS
Iron has two common oxidation states (+2 and +3) in,
for example, Fe2+ and Fe3
Manganese has a very wide range of oxidation states
in its compounds. For example:
+2 in Mn2+
+3 in Mn2O3
+4 in MnO2
+6 in MnO42-
+7 in MnO4-
The diagrams show aproximate colours for some
common transition metal complex ions.
Magnetic Properties
 On the basis of behaviour in a magnetic field, substance are
classified as paramagnetic, diamagnetic and ferromagnetic.
Those substance which are attracted by the applied
magnetic field are called paramagnetic where as those
which are repelled by the magnetic field are called
diamagnetic.
 Paramagnetism is a property due to the presence of

unpaired electrons. Thus most of the transition metals are
paramagnetic. As the number of unpaired electrons
increases, the paramagnetic character also increases.
THE ORIGIN OF COLOUR IN THE
TRANSITION METAL IONS
When white light passes through a

solution of one of these ions, or is
reflected off it, some colours in the
light are absorbed. The colour you see
is how your eye perceives what is left.
Attaching ligands to a metal ion has an

effect on the energies of the d orbitals.
Light is absorbed as electrons move
between one d orbital and another.
CATALYTIC ACTIVITY
Transition metals and their

compounds are often good
catalysts. Transition metals and
their compounds function as
catalysts either because of their
ability to change oxidation state
or, in the case of the metals, to
adsorb other substances on to
their surface and activate them in
the process.
REDUCING VANADIUM(V) IN STAGES TO
VANADIUM(II)
The usual source of vanadium in the +5
oxidation state is ammonium metavanadate,
NH4VO3. This isn't very soluble in water and is
usually first dissolved in sodium hydroxide
solution. The solution can be reduced using zinc
and an acid - either hydrochloric acid or
sulphuric acid, usually using moderately
concentrated acid.
The reaction is done under acidic conditions
when the main ion present is VO2+ - called the
dioxovanadium(V) ion.
The reduction is shown in two stages. Some
individual important colours are shown, but the
process is one continuous change from start to
finish.
The reduction from +5 to +4
The reduction from +4 to +2
The colour changes just continue.
WHAT IS A COMPLEX METAL
ION?
A complex ion has a metal ion
at its centre with a number of
other molecules or ions
surrounding it. These can be
considered to be attached to
the central ion by co-ordinate
(dative covalent) bonds.
The molecules or ions
surrounding the central
metal ion are called
LIGANDS.
The table shows some common ligands and the code for
them in the name of a complex ion.
ligand coded by (old name)

H2O aqua aquo
NH3 ammine ammino

OH- hydroxo hydroxy
Cl- chloro
F- fluoro
CN- cyano
Coding for the number of ligands
The normal prefixes apply if there is more than one
ligand.
no of ligands coded by
2 di
3 tri
4 tetra
5 penta
6 hexa
Putting this together
For a complex ion containing only one
type of ligand, there is no problem. For
example:
[Cu(H2O)6]2+ is called the
hexaaquacopper(II) ion.
[Cu(NH3)4(H2O)2]2+ is called the
tetraamminediaquacopper(II) ion.
The "ammine" is named before the
"aqua" because "am" comes before "aq"
in the alphabet. The "tetra" and "di" are
ignored.
Naming the metal
It depends on whether the complex ion ends up as
positively or negatively charged.
•For positively charged complex ions. A positively

charged complex ion is called a cationic complex.
A cation is a positively charged ion.The metal in
this is named exactly as you would expect, with
the addition of its oxidation state.
•For negatively charged complex ions. A

negatively charged complex ion is called an
anionic complex. An anion is a negatively charged
ion.In this case the name of the metal is modified
to show that it has ended up in a negative ion.
This is shown by the ending -ate.
Common examples include:
metal changed to
cobalt cobaltate
aluminium aluminate
chromium chromate
vanadium vanadate
copper cuprate
iron ferrate
SOME SIMPLE SHAPES FOR
COMPLEX IONS
These shapes are for
complex ions formed using
monodentate ligands -
ligands which only form one
bond to the central metal
ion.
6-CO-ORDINATED COMPLEX IONS
These are complex ions in which the

central metal ion is forming six
bonds, that means that it will be
attached to six ligands. These ions
have an octahedral shape. Four of
the ligands are in one plane, with the
fifth one above the plane, and the
sixth one below the plane.
The diagram shows four fairly random examples of
octahedral ions
4-CO-ORDINATED COMPLEX IONS
These are far less common, and they can take up one of two
different shapes.
Tetrahedral ions
There are two very similar ions which crop up commonly at this
level: [CuCl4]2- and [CoCl4]2-.
The copper(II) and cobalt(II) ions have four chloride ions bonded
to them rather than six, because the chloride ions are too big to
fit any more around the central metal ion.
A SQUARE PLANAR COMPLEX
Occasionally a 4-co-ordinated complex turns out to be
square planar. There's no easy way of predicting that this
is going to happen. Cisplatin is a neutral complex,
Pt(NH3)2Cl2. It is neutral because the 2+ charge of the
original platinum(II) ion is exactly cancelled by the two
negative charges supplied by the chloride ions.
WHY DO WE SEE SOME COMPOUNDS AS BEING
COLOURED?
White light
If you pass white light through a prism it splits
into all the colours of the rainbow. Visible light
is simply a small part of an electromagnetic
spectrum most of which we can't see - gamma
rays, X-rays, infra-red, radio waves and so on.
Each of these has a particular wavelength,

ranging from 10-16 metres for gamma rays to
several hundred metres for radio waves. Visible
light has wavelengths from about 400 to 750
nm. (1 nanometre = 10-9 metres.)
The diagram shows an approximation to the
spectrum of visible light.
Why is copper(II) sulphate solution blue?
If white light (ordinary sunlight, for

example) passes through copper(II)
sulphate solution, some wavelengths in
the light are absorbed by the solution.
Copper(II) ions in solution absorb light in
the red region of the spectrum.
The light which passes through the
solution and out the other side will have
all the colours in it except for the red. We
see this mixture of wavelengths as pale
blue (cyan).
The diagram gives an impression of what
happens if you pass white light through
copper(II) sulphate solution.
Red + Yellow makes Orange
Yellow + Blue makes Green
Blue + Red makes Violet
THE ORIGIN OF COLOUR IN COMPLEX
IONS CONTAINING TRANSITION
METALS
Complex ions containing transition
metals are usually coloured, whereas
the similar ions from non-transition
metals aren't. That suggests that the
partly filled d orbitals must be involved
in generating the colour in some way.
Remember that transition metals are

defined as having partly filled d
orbitals.
The diagram shows the arrangement of the d
electrons in a Cu2+ ion before and after six water
molecules bond with it.
Whenever 6 ligands are arranged
around a transition metal ion, the d
orbitals are always split into 2 groups
in this way - 2 with a higher energy
than the other 3.
The size of the energy gap between

them (shown by the blue arrows on the
diagram) varies with the nature of the
transition metal ion, its oxidation state
(whether it is 3+ or 2+, for example),
and the nature of the ligands.
The diagrams show some approximate colours of some
ions based on chromium(III).
For example, a commonly quoted case comes from
cobalt(II) chemistry, with the ions [Co(H2O)6]2+ and
[CoCl4]2-.
Chloride ions are bigger than water molecules, and there

isn't room to fit six of them around the central cobalt ion
This reaction can be easily reversed by adding water to
the solution. Adding water to the right-hand side of the
equilibrium has the effect of moving the position of
equilibrium to the left. The pink colour of the
hexaaquacobalt(II) ion is produced again (only paler, of
course, because it is more dilute).
Replacing the water in the hexaaquacopper(II) ion
The colour of the tetrachlorocuprate(II) ion is almost
always seen mixed with that of the original hexaaqua
ion.
What you normally see is:
The reaction taking place is reversible, and you get a

mixture of colours due to both of the complex ions.

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TRANSITION METALS

The elements in the Periodic Table which correspond to

The 2+ ion is formed by the loss of the two 4s electrons.

 Paramagnetism is a property due to the presence of

When white light passes through a

Attaching ligands to a metal ion has an

Transition metals and their

ligand coded by (old name)

NH3 ammine ammino

•For positively charged complex ions. A positively

•For negatively charged complex ions. A

These are complex ions in which the

Each of these has a particular wavelength,

If white light (ordinary sunlight, for

Remember that transition metals are

The size of the energy gap between

Chloride ions are bigger than water molecules, and there

The reaction taking place is reversible, and you get a

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