Tranition metals Flashcards
What are transition metals
D block elements that have an ion with an incomplete d subshell.
Electron configuration of chromium
3d5 4s1
Electron configuration of copper
3d10 4s1
Transition elements form compounds in which they have different oxidation states
For example Iron forms two different chlorides, Iron (2) chloride Fe2Cl and Iron (3) chloride Fe3Cl.
Transition elements form coloured compounds
Potassium dichromate is bright orange and Nickel (2) sulfate is green.
Transition elements and their compounds can act as a catalyst
Iron is used in the haber process to make ammonia from nitrogen and hydrogen. Nickel is used as a catalyst in the hydrogenation of alkenes, for example making margarine.
A ligand
A molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond (dative covalent bond)
A dative covalent bond or coordinate bond
A special kind of covalent bond, formed when one of the bonded atoms provides both of the electrons in a shared pair
Coordinate number
Indicates the number of coordinate bonds attached to the central metal ion
Example of a complex ion
[Cr(H2O)6] 2+
Monodentate ligand
Only donates one pair of electrons
Bidante ligand
Donates two pairs of elecrons to the central metal ion.
Octohedral complex ion
Has a coordinate number of 6, bond angle of ninety degrees
Tetrahedral complex ion
Most common shape for a complex ion with a coordinate number of four, bond angle is 109.5
Square planar complex ion
Bond angle of ninety degrees, occurs with 8d elements ie platinum, gold and palladium
Optical isomerism in octahedral complexes
Optical isomerism only occurs in octahedral complexes containing two or more bidente ligands. They are mirror images of each other, like a left and right hand
Cis-platin drug
This is an anti-cancer drug which works by forming a platinum complex and binding to DNA and preventing it from replication. Activation of a cells own repair mechanism eventually leading to the death of the cancer containing cell.
Cis isomerism square planar
Where the two identical groups are adjacent to each other, they are at ninety degrees to each other
Trans isomerism square planar
When the two identical groups are opposite each other and are at 180 degrees to each other
Monodentate ligands in octahedral complexes cis-trans
The cis isomerism has two identical groups adjacent to each other, they are at ninety degrees to each other. In the trans isomerism they are opposite each other and are 180 degrees apart.
Bidentate ligand in octahedral complexes cis-trans
In cis they are adjacent, in trans they are opposite
Ligand substitution
A reaction where one ligand in a complex ion is replaced by another ligand.
Reaction of copper sulphate with ammonia
A pale blue precipitate of Cu(OH)2 is formed when only a couple of drops of ammonia is added. This precipitate then dissolves in excess ammonia to form a dark blue soloution
Equation of copper hydroxide and ammonia
[Cu(H2O)6]2+(aq) + 4NH3(aq) —> [Cu(NH3)4(H2O)2]+2(aq) + 4H2O(l)
In this reaction 4 ammonia ligands have replaced 4 water ligands
Reaction of copper with concentrated hydrochloric acid
A pale blue soloution changes colour to form a yellow soloution.
Equation of copper with HCl
[Cu(H2O)6]2+(aq) + 4Cl-(aq) –> [CuCl4]2-(aq) + 6H2O(l)
Haemoglobin and oxygen
Haemoglobin is composed of four polypeptide chains. Each chain contains haem which has Fe2+ at its centre, oxygen can bing to haem and transport it round the body where it can be released, from the lungs. The haemoglobin can then carry CO2 back to the lungs.
Haemoglobin and Carbon monoxide
CO binds more strongly to haemoglobin then O2. Leaving fewer haemoglobin molecules to bind to oxygen. Tissues can be starved of oxygen because less oxygen is carried round the body. This is an example of ligand substitution as CO molecules can replace oxygen molecules in haemoglobin. This reaction is not reversible and can lead to death
Precipitation reaction
A reaction in which soluble ions, in separate solutions, are mixed together to produce an insoluble compound which forms a solid
Precipitation reaction between Cu2+ and NaOH
Blue precipitate forms which is insoluble in excess NaOH
Cu2+(Aq) + 2OH-(aq) —> Cu(OH)2
[Cu(H2O)2+(aq) + 2OH-(aq) —> Cu(OH)2(H2O)4 +2H2O
Precipitation reaction of Cu2+ with ammonia
A blue precipitate forms which re-dissolves to form a blue soloution
[Cu(H2O)6]2+(aq) + 2NH3(aq) —> Cu(OH)2(H2O)4 + 2NH4+(aq)
Precipitation reaction of Fe2+ and NaOH
Pale green soloution reacts to form a green precipitate of Iron(2) hydroxide. Insoluble in excess NaOH but turns brown on the surface as Iron(2) is oxidised to Iron(3)
Fe2+(aq) + 20H-(aq) –>Fe(OH)2(s)
in air
Fe(OH)2(s) –>Fe(OH)3(s)
Precipitation reaction of Fe2+ with ammonia
Reacts in the same way as with aqueous NaOH forming Fe(OH)2(s)
Precipitation reaction of Fe3+ and NaOH
Pale yellow soloution reacts to form an orange-brown precipitate of Iron(3) hydroxide, the precipitate is insolouble in excess NaOH
Fe3+(aq) + 3OH-(aq) –>Fe(OH)3(s)
Precipitation reaction of Fe3+ and NaOH
Reacts in the same way as with aqueous NaOH forming Fe(OH)3(s)
Precipitation reaction of Mn2+ and NaOH
Pale pink soloution reacts to form a light brown precipitate of manganese(2) hydroxide which darkens on standing in air. The precipitate is insolouble in excess NaOH
Mn2+(aq) + 2OH-(aq) –>Mn(OH)2(s)
Precipitation reaction of Mn2+ with ammonia
Reacts in the same way as with aqueous NaOH forming Mn(OH)2(s)
Precipitation reaction of Cr3+ with NaOH
Violet soloution reacts to form a grey-green precipitate of chromium(3) hydroxide. The precipitate is solouble in excess NaOH forming a dark green soloution
Cr3+(aq) + 3OH-(aq) –> Cr(OH)3(s)
Cr(OH)3(s) + 3OH-(aq) –> [Cr(OH)6]3-(aq)
Precipitation reaction of Cr3+ with ammonia
Cr(OH)3 is a green precipitate which dissolves in excess ammonia to form [Cr(NH3)6]3+(aq) which is a purple soloution
