Transition Metals
Transition metals are contained within the d block of the periodic table as their outermost electron is
in the d sub shell.
TRANSITION METAL – A metal that can form one or more stable ions with an incomplete d sub-level.
Chromium and copper have electron configurations that are different to what would be expected,
chromium has one electron in each 3d orbital but has only 1 electron in its 4s orbital. Copper has a full
3d orbital but only has 1 electron in its 4s electron. This makes both of the atoms more stable.
Scandium and zinc are not transition metals as they don’t have incomplete 3d sub levels in their stable
ions. Scandium 3+ has an empty 3d orbital and Zinc 2+ has a full 3d sub level. This occurs because the
electrons are removed from the 4s orbital as this has a lower energy level than 3d.
Transition metals all have a high density and have high melting and boiling points. The chemical
properties of transition metals are that they form complex ions, they form coloured ions, they are
good as catalysts and can exist in variable oxidation states. Transition metals have variable oxidation
states as the energies of the 4s and 3d sub levels are similar, so different numbers of electrons can be
gained or lost using similar amounts of energy.
The incomplete d sub level accounts for the chemical properties of transition metals.
COMPLEX ION – A metal ion surrounded by coordinately bonded ligands
COORDINATE BOND – A coordinate bond in which both electrons in the shared pair come from one
atom
LIGAND – An atom, ion or molecule that donates a pair of electrons to a central metal ion
Ligands can form varying numbers of coordinate bonds with the central metal ion, dependent on the
number of lone pairs that are on the molecule:
- Monodentate; a ligand that can form 1 coordinate bond with the central metal ion
- Bidentate; a ligand that can form 2 coordinate bonds with the central metal ion
- Multidentate; a ligand that can form many coordinate bonds with the central metal ion.
Examples of each of the type of ligand are:
- Monodentate; Cl-, NH3, H2O
- Bidentate; (en) C2O42-
- Multidentate; EDTA4-
The oxidation state of the transition metal ion can be calculated by taking the sum of the charges of
the ligands from the total charge of the complex ion.
The shape of a complex ion depends on its coordination number which is the number of coordinate
bonds that have been formed by ligands with the central metal ion.
- Molecules with 6 coordinate bonds have an octahedral shape with bond angles of 90
- Molecules with 4 coordinate bonds have a tetrahedral shape with bond angles of 109.5 or a
square planar shape with bond angles of 90
- Molecules with 2 coordinate bonds have a linear shape with bond angles of 180.
Optical isomerism can occur in octahedral complexes with 3
bidentate ligands bonded to the central metal ion. Two non-
superimposable mirror images can be formed due to the
arrangement of the bonding of the bidentate ligands.
Transition metals are contained within the d block of the periodic table as their outermost electron is
in the d sub shell.
TRANSITION METAL – A metal that can form one or more stable ions with an incomplete d sub-level.
Chromium and copper have electron configurations that are different to what would be expected,
chromium has one electron in each 3d orbital but has only 1 electron in its 4s orbital. Copper has a full
3d orbital but only has 1 electron in its 4s electron. This makes both of the atoms more stable.
Scandium and zinc are not transition metals as they don’t have incomplete 3d sub levels in their stable
ions. Scandium 3+ has an empty 3d orbital and Zinc 2+ has a full 3d sub level. This occurs because the
electrons are removed from the 4s orbital as this has a lower energy level than 3d.
Transition metals all have a high density and have high melting and boiling points. The chemical
properties of transition metals are that they form complex ions, they form coloured ions, they are
good as catalysts and can exist in variable oxidation states. Transition metals have variable oxidation
states as the energies of the 4s and 3d sub levels are similar, so different numbers of electrons can be
gained or lost using similar amounts of energy.
The incomplete d sub level accounts for the chemical properties of transition metals.
COMPLEX ION – A metal ion surrounded by coordinately bonded ligands
COORDINATE BOND – A coordinate bond in which both electrons in the shared pair come from one
atom
LIGAND – An atom, ion or molecule that donates a pair of electrons to a central metal ion
Ligands can form varying numbers of coordinate bonds with the central metal ion, dependent on the
number of lone pairs that are on the molecule:
- Monodentate; a ligand that can form 1 coordinate bond with the central metal ion
- Bidentate; a ligand that can form 2 coordinate bonds with the central metal ion
- Multidentate; a ligand that can form many coordinate bonds with the central metal ion.
Examples of each of the type of ligand are:
- Monodentate; Cl-, NH3, H2O
- Bidentate; (en) C2O42-
- Multidentate; EDTA4-
The oxidation state of the transition metal ion can be calculated by taking the sum of the charges of
the ligands from the total charge of the complex ion.
The shape of a complex ion depends on its coordination number which is the number of coordinate
bonds that have been formed by ligands with the central metal ion.
- Molecules with 6 coordinate bonds have an octahedral shape with bond angles of 90
- Molecules with 4 coordinate bonds have a tetrahedral shape with bond angles of 109.5 or a
square planar shape with bond angles of 90
- Molecules with 2 coordinate bonds have a linear shape with bond angles of 180.
Optical isomerism can occur in octahedral complexes with 3
bidentate ligands bonded to the central metal ion. Two non-
superimposable mirror images can be formed due to the
arrangement of the bonding of the bidentate ligands.
