Topic 15 - TRANSITION METALS
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Definition of a transition metal
An element that has an incomplete d sub shell in its common ions
Which two period 4 d-block elements are not transition metals and why? (6)
• Transition metals are elements that have an incomplete d sub shell in its common ions • Scandium forms Sc3+ ion • Electronic configuration of Sc3+: 1s2 2s2 2p6 3s2 3p6 • In Sc3+, the d orbital is empty • Zinc forms Zn2+ ion • Electronic configuration of Zn2+: 1s2 2s2 2p6 3s2 3p6 3d10 • In Zn2+, the d orbital is completely full • Therefore Zn and Sc are not transition metals
Electronic configuration of Cr using [Ar]
[Ar] 4s1 3d5
Electronic configuration of Cu using [Ar]
[Ar] 4s1 3d10
Describe and explain the properties of a transition metal
• High MP/BP • High density • High tensile strength • Large nuclear charge • Small atomic radius • Strong electrostatic attraction
Why do transition metals have variable oxidation states?
• Energy difference between orbitals • So both energy levels can be used for bond formation
Why do transition metals form coloured compounds?
• Gap in energy levels between d orbitals • Electrons absorb energy to be promoted to higher energy level • We see colour because of the visible light that is not absorbed • The colour we see of solids is due to light being reflected
Identify 4 factors that affect the colour of transition metal complexes and explain why they affect colour
• Oxidation state • Ligands • Co ordination number • Shape All affect size of energy gap between d orbitals and wavelength of light absorbed
What does this equation stand for: △E = hf = hc/λ
△E = gap in energy h = Planck’s constant (6.63 x 10^-34 J) f = frequency of light c = velocity of light λ = wavelength of light
Definition of a ligand
Particle with lone pair of electrons that bonds to metals by a co-ordinate bond
Definition of a complex
Metal ion with co-ordinately bonded ligands
Definition of co-ordinate number
Number of co-ordinate bonds from ligands to metal ion
What is the shape and angle of a complex with: - Coordination number: 2 - Contains Ag+ ?
• Planar • 180
What is the shape and angle of a complex with: - Coordination number: 4 - Contains Pt 2+ and Ni 2+ ?
• Square planar • 90
What is the shape and angle of a complex with: - Coordination number: 4 - Contains larger ligands eg Cl- ?
• Tetrahedral • 109.5
What is the shape and angle of a complex with: - Coordination number: 6 - Contains small ligands eg. H2O ?
• Octahedral • 90
What is a monodentate ligand and give examples?
• Ligand which has one pair of electrons they can donate to a central metal ion • H2O • NH3 • Cl- • CN-
What is a bidentate ligand?
• Ligand which can form two dative bonds to the complex ion as it contains two lone pairs of electrons
What is a polydentate ligand and give examples?
• Ligand with more than two atoms with lone pairs of electrons and can form more than two dative bonds to the complex ions • EDTA+
How can we identify cisplatin complexes from a diagram?
Similar ligands are next to each other
How can we identify transplatin complexes?
Similar ligands are opposite each other
What is a ligand substitution?
A reaction where one ligand is replaced by another ligand
What is the colour of [Cu(H2O)6]2+
Blue
What is the colour of [Fe(H2O)6]2+
Green