elements with an incomplete d-subshell that can form at least one stable ion with an incomplete sub shell
Electron configuration of chromium
[Ar] 4s1 3d5
Electron configuration of copper
[Ar] 4s1 3d10
Why do chromium and copper have different electron configurations than the pattern
As half full and full d-subshells are energetically more stable
Properties of transition elements
-Variable oxidation states-Form complex ions-Form coloured compounds-Behave as catalysts
Complex ion
A transition metal ion bonded to one or more ligands by coordinate bonds
How can transition elements act as catalysts?
They can change oxidation states by gaining or losing electrons within their d orbitals. This means they can transfer electrons to speed up reactions. They are good at adsorbing substances onto their surfaces to lower the activation energy.
Co-ordination number
The number of co-ordinate bonds formed to a central metal ion
Monodentate ligand
Can form one dative covalent bond to the central metal ion
Bidentate ligand
Can form two dative covalent bonds to the central metal ion as it containing 2 atoms with lone pairs of electrons
Octahedral complexes
6 coordinate bonds, 90 bond angles
Tetrahedral complexes
4 coordinate bonds, 109.5° bond angles
Square planar complexes
4 coordinate bonds, 90° bond angles, only for Ni, Pd and Pt
Optical isomer
Non-superimposable mirror images
Complex ions with optical isomerism
Octahedral complexes with bidentate ligands
How cis-platin acts as an anti-cancer drug
Binds to cystine and guanine which distorts the shape of DNA and prevents DNA replication so mitosis can't occur
Adverse effects of cis-platin as a cancer drug
Binds to healthy cells so can cause side-effects such as hair loss
Ligand substitution
When one ligand in a complex is replaced by another
Ligand substitution makes complexes more stable than the original
Ligand substitution does not change the coordination number and geometry if the ligands are a similar size, if there is a large difference in size like water and chlorine, the coordination number and geometry will change
Transition element ion in solution
Is a hexaaqua complex ion
Why does the coordination number and geometry change in the reaction from hexaaqua copper(II) to [CuCl4]2-?
As chloride ions are larger that water molecules so only 4 are able to bond to the central metal ion, geometry changes from octahedral to tetrahedral
Number of OH-substituted is the same as the charge on the initialion