5.3.1 Transition Elements Flashcards
define Ligand
An ion or molecule that co-ordinately bonds to central metal ions by donating a lone pair of electrons
what is a complex ion?
A complex ion is a Metal ion surrounded by co-ordinately bonded Ligands
Define coordinate bonds
Coordinate bonds are bonds where both electrons come from one of the participating atoms
what is an octahedral complex ion? Draw one and give the bond angle
It is a metal ion co-ordinately bonded to six ligands with a bond angle of 90
what is a tetrahedral complex ion? draw it and give the bond angle
It’s a metal ion bonded to 4 ligands with a bond angle of 109.5
It has 2 straight lines, one cone and one dotted
what is a square planar complex ion? draw it and give the bond angle
A metal ion co-ordinately bonded to 4 ligands with a bond angle of 90
happens only in Pt Co Cu Zn
2 behind and 2 in front
why are zinc and scandium d-block elements but not transition elements
this is because their ions do not have partially filled d-blocks, while the definition of a transition metal is a metal that can make ions with an incomplete d-sub-shell
define precipitation reaction
a reaction in which soluble ions from two solutions are mixed to produce an insoluble ionic solid (precipitate)
give the electron configuration of the d-block elements:
- Scandium
- chromium
- Iron
- Copper
- Zinc
- Sc 1s2 2s2 2p6 3s2 3p6 4s2 3d1
-Cr 1s2 2s2 2p6 3s2 3p6 4s1 3d5
-Fe 1s2 2s2 2p6 3s2 3p6 4s2 3d5
-Cu 1s2 2s2 2p6 3s2 3p6 4s1 3d10
Zn 1s2 2s2 2p6 3s2 3p6 4s2 3d10
What are some properties of transition elements?
- being able to have more than one oxidation state in its compounds
- the ability to form colored ions
- being able to act as a catalyst
what is a bidentate ligand?
- molecules able to form 2 coordinate bonds with a central metal ion as it has 2 lone pairs of electrons
what is a coordinate number?
a number representing the amount of ligands present
what are the types of isomerism shown by complex ions?
- cis/trans isomerism
- Optical isomerism
do some transition metal isomersim questions!
notes:
https://pmt.physicsandmathstutor.com/download/Chemistry/A-level/Notes/AQA/Inorganic-II/Detailed/2.5.%20Transition%20Metals.pdf
what are the uses of cis platins?
cancer treatement
what is a disproportionation reaction?
A disproportionation reaction is one in which a single substance is both oxidised and reduced
what is a platin?
A platin is a transitional metal complex with the Formula
PtCl2(NH3)2
and so is a square planar molecule
the CL- and Nh3 molecles act as ligands
what is a platin?
A platin is a transitional metal complex with the Formula
PtCl2(NH3)2
and so is a square planar molecule
the CL- and Nh3 molecles act as ligands
what is the oxidation number of platinum in the cis platin?
2+
what is the shape and bond angle of the cis patin complex?
they are square planar and have a bond angle of 90
draw and name both geomatrical isomers of a platin
Cis-platin has 2 same groups next to eachother
trans platin has same groups opposite eachother
why are cis-platins used for cancer treatment? and explain the process
It diffuses the tumourcell membrane as it has no charge
when it enters the cell, cis platin undergoes ligand substitution and exchanges a chloride ion for a h20 molecule
this now positively charged complex binds to DNA in the nucleus changing its shape making it unable to replicate
results in the tumour being destroyed if enough canerous cells absorb cis-platins
what are the features of haemoglobin?
A globular protein containing 4 protein chains
each chain contains a haem molecule whose central metal ion is the haem group Fe2+
how does oxygen bind to haemoglobin?
as blood passes through the lungs, haemoglobin coordinatly bonds to the oxygen due to increased oxygen pressure forming Oxyhaemoglobin which releasess o2 to cells
how does carbon MONOXIDE bind with Haemoglobin
carbon monoxide can act as a ligand and form a coordinate bond with the fe2+ ion in haemoglobin
a ligand substitiution reaction occurs replacing the 02 with carbon monoxide because the bond of C0 is stronger with heam than 02
this stops haemoglobin from transporting o2 around the body and thus carbon monoxide poisoning
how do Cu2+ ion in solution react with aqueous sodium hydroxide?
blue solution reacts to form a blue precipitate – insoluble in excess sodium hydroxide
how do Fe2+ ions in solution react with aqueous sodium hydroxide?
pale green solution reacts to form a green precipitate – turns rusty brown on surface on standing in air – precipitate is insoluble in excess sodium hydroxide
how do Fe3+ ions in solution react with aqueous sodium hydroxide?
pale yellow solution forms a rusty brown precipitate – precipitate is insoluble in excess sodium hydroxide
how do Mn2+ ion in solution react with aqueous sodium hydroxide?
pale pink solution reacts to form a brown precipitate –precipitate is insoluble in excess sodium hydroxide
how do Cr3+ ions in solution react with aqueous sodium hydroxide?
violet solution reacts to form a grey-green precipitate – precipitate, dissolves in excess NaOH to form a dark green solution
how do you represent transition metal ions as a complex in solution ?
show Cu2+ and its reaction with sodium hydroxide (NaOH)
show the equation
Cu2+ = [Cu(H20)6]2+
so the precipitation reaction can be shown as:
[Cu(H20)6]2+(aq) + 2OH-(aq) —> Cu(OH)2(H20)4 + 2 H20(l)
wtrite out the ionic equation for the reaction of [Cu(H20)6]2+ and NaOH
1) write out the chemical equation in terms of ions, leave solids and compound ions as they are
2) cross out spectator ions not involves in the reaction
this leaves you with
Cu2+(aq) +2OH-(aq) —>Cu(OH)2(s)
EXCEPTION: CHROMIUM ION in ppt reactions
what is the reaction of Chromium reacting with NaOH and then redissolving its precipitate?
[Cr(H20)6]3+ —> [C(H20)3(OH)3]
—> [Cr(OH)6]3-
how do Cu2+ ions in solution react with aqueous ammonia?
blue solution reacts to form a blue precipitate – dissolves in excess ammonia to form a dark blue solution
how do Fe2+ ions in solution react with aqueous ammonia?
pale green solution reacts to form a green precipitate – turns rusty brown on surface on standing in air – precipitate is insoluble in excess ammonia
how do Fe3+ ions in solution react with aqueous ammonia?
pale yellow solution forms a rusty brown precipitate – precipitate is insoluble in excess ammonia
how do Cr3+ ions in solution react with aqueous ammonia?
violet solution reacts to form a grey-green precipitate – precipitate dissolves in excess ammonia to form a purple solution
how do Mn2+ ions in solution react with aqueous ammonia?
pale pink solution reacts to form a brown precipitate – turns rusty brown on surface on standing in air – precipitate is insoluble in excess ammonia
why does the reaction of aqueous ammonia work in precipitate reactions?
Ammonia acts as a proton acceptor (base) and take a H+ ion from water, leaving an OH- still coordinately bonded to the metal ion
how do you write the equation for a reaction of a metal ion in solution with ammonia?
Try Cu2+ ion
[Cu(H20)6]2+(aq) + 2NH3 (aq)
—>[Cu(OH)2(H20)4] (s)+ 2NH4+(aq)
you can also write Cu2+(aq) +2OH-(aq) —> Cu(OH)2(s)
which ions redissolve their precipitates when excess ammonia is added and why?
Copper and Chromium
this is becase initially ammonia acts as a base, accepting a H+ ion from the H2O molecules leaving an OH- ion in the process, with excess ammonia the complex undergoes a LIGAND SUBSTITUTION REACTION replacing the OH- with ammonia ions to act as a ligand and producing water
what is a redox reaction?
A reaction where both oxidation and reduction take place simultaneously
what is a reducing agent?
The reducing agent gives electrons to species being reduced and is itself oxidised.
what is an oxidising agent?
The oxidising agent takes electrons from the species being oxidised and is itself reduced
what are the steps in writing (a-level) half equations?
try this with N2—>NO3- and Cr2O7 2- —->Cr3+
remember to balance it
- Balance the equation in terms of atoms (not including oxygen and hydrogen)
- Work out the oxidation numbers of the species being oxidised or reduced
- Balance the electrons using the oxidation numbers
- Balance the number of oxygen atoms by adding in water molecules (H2O)
- Balance the number of hydrogen atoms by adding in hydrogen ions (H+)
you can write a full equation by combining the half equations and making sure the electrons transferred are equal. How do you do it?
mae sure electrons on both sides are the same
combine both equations
simplify by elimination all H20 and H+ ions
what is the redox colour change of Cr3+?
Cr3+ = green in 3+ oxidation state
what is the redox colour change of CrO4^2- ⇌ Cr2O7^2-
yellow ⇌ orange
both have oxidation states of +6
what is the colour redox change of
MnO4-
purple
what is the redox colour change of Mn^2+
colourless
what is the redox colour change of Cu^2+
blue
what is the redox colour change of Fe^2+
pale green
what is the redox colour change of Fe^3+
yellow-brown
