Transition metals Flashcards
What is a d block transition metals
A metal which for at least one of its ions has an incomplete d sub shell.
Difference in orbital filling rules for transition metals
For copper and chromium (number 4 and 9) having a half filled or filled 3d sub shell is more stable than a 4s sub shell, so the last electron goes into the 3d sub shell.
Difference in ions formed in transition metals
In transition metals the 4s electrons are lost before the 3d electrons .
Oxidation number rules
Uncombined elements have ON =0
Ions of single atoms have ON equal to charge
Oxygen has ON = -2 in compounds
In its compounds hydrogen has ON=+1
Compounds ON =0
Polyatomic ions ON= charge
Oxidation state
The oxidation number in Roman numerals
Oxidation number or state of individual ion in compound
Calculate oxidation number of other ion,
make it equal to the individual ion
Take away or add charge.
Oxidation effect on oxidation number
Increase
Reduction effect on oxidation number
Decrease
Transition metals oxidation states
Have variable oxidation states with different stability
High oxidation states
Oxidising agents
Low oxidation states
Reducing agents.
Transition metal complex definition
A central metal atom or ion surrounded by ligands which have formed dative covalent bonds with the metal.
Ligand’s definition
Molecules or negative ions with non bonding electrons which they donate to the unfilled d sub shell
Common ligands ( negative ions)
Cl-
CN-
OH-
Common ligands (molecules)
H2O, NH3
Process of ligand forming covalent bond
The ligands non bonded electron pair will donate both electrons to the metal ions orbital and form a dative covalent bond.
Dative covalent bond
A covalent bond formed by a ligand donating a non bonded electron pair.
Dative bond properties
Identical to other covalent bonds after formed.
Types of ligand
Monodentate
Bidentate
Hexadentate
Monodentate ligand
A ligand which donates one set of non bonded electrons
Bidentate ligand
A ligand which donates two sets of non bonded electrons
Hexadentate ligand
A ligand which donates 6 non bonded electron pairs
Monodentate examples
OH2
NH3
CN-
OH-
F-
Cl-
Bidentate examples
O2C2O2 2- oxalato
1,2-diaminoethane
Hexadentate examples
EDTA
Co-ordination number
The number of bonds between a ligand and a metal.
(Count)
Iupac rules
The rules for naming metal complexes
Metal complexes definition
A metal atom or ion bonded to ligands
Rules for IUPAC formula
[metal ligandA ligandB]
Ligands are ordered alphabetically based on element which donates non bonded electron pair.
Rules for IUPAC naming
Ligands are named alphabetically followed by
metal and oxidation state
Suffix e is now o
Water is aqua, ammonia is ammine and carbon monoxide is carbonyl
If negative oxidation state the metals suffix is -ate and iron is ferrite and copper is cuprate.
How are metal complexes coloured
A metal complexes ligands will cause 3d orbital splitting which will allow electrons to be promoted from the lower 3d orbital to the higher 3d orbitals, this will allow the metal complex to absorb visible wavelengths of light and reflect complimentary wavelengths of light.
Higher energy 3d orbitals
dx2-y2 and dz2
Lower energy 3d orbitals
dxy, dxz, dyz
Order of ligands from strong to weak
CN-, NH3, OH2 OH- F- Cl- Br- I-
Strong field ligands
Ligands that cause a large energy gap between the upper and lower 3d orbitals, meaning more energy is needed for the d-d orbital transition.
Weak field ligands
Ligands that cause a small energy gap between the upper and lower 3d orbitals meaning less energy is needed for the d-d orbital transition.
What region of light do strong field ligands absorb
Ultraviolet light.
Uv wavelengths of light
200 to 400nm
Visible wavelengths of light
400 to 700nm
What are typical catalysts
Transition metals
Types of catalysts
Homogenous and heterogenous
Homogenous catalyst
A catalyst which is in the same state as the reactants.
Heterogenous catalyst
A catalyst which id in a different state to the reactants.
How do heterogenous catalysts work
Reactant molecules approach the surface of the catalyst.
Due to the unfilled d orbitals in the catalyst the reactants form activated complexes and bond with the catalyst - this is known as adsorption .
The bonds between reactant molecules rearrange.
Product molecules will leave the surface of the catalyst.
How do homogenous catalysts work
Homogenous catalysts change the oxidation state to make a reactant molecule more reactive and react faster.
Absorption definition
Where reactant molecules collide with the surface of a heterogenous catalyst and stick to it
How does absorption on heterogenous catalysts work
The presence of unfilled d orbitals allows the molecules to form activated complexes between the reactant and catalyst.
