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36 Cards in this Set
- Front
- Back
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Transition metals definition |
A metal that can form one or more stable ions with an incomplete d sub-shell |
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When doing the electronic configuration of transition metals |
Fill lowest energy levels fully first eg. 4s before 3d except 1)chromium fills each 3d orbital once and leaves one electron in 4s this is more stable due to less repulsion then having 2 electrons in 4s 2)Copper fills 3d fully then leaves one electron in 4s again for more stability |
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When transition metals form ions they lose electrons from which sub level first |
4s |
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Why aren’t scandium and zinc considered transition metals |
Although they are in the d block they don’t form stable ions with an incomplete d sub shell. Scandium forms sc3+ with an empty 3d sub level . Zinc forms one stable ion zn2+ with a full d sub shell . Therefore both aren’t transition metals |
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Physical properties of transition metals |
(Typical metals) -high density -high melting/boiling point -lustrous and malleable |
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Chemical properties |
-form complex ions -form coloured ions -good catalyst -variable oxidative states |
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A complex ions is |
Is a metal ion surrounded by coordinately bonded ligands |
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What are Ligands |
Atoms ions or molecules that donate a pair of electrons t a central metal ion |
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Ligands donate different numbers of electron pairs |
Monodentate = one pair Bidentate=two pairs Multidentate= two or more pairs |
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How to work out oxidation state of metals in complex ions can be worked out using |
Total charge of complex - sum of the charges of the Ligands |
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Shapes of complexes |
6 co-ordinate bonds = octahedral shape 4 co-ordinate bonds= tetrahedral /square planar 2 co-ordinate bonds = linear |
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What is optical isomerism |
A type of stereo isomerism (same molecular formula with bonds arranged differently in space) it has two enatiomers which are non superimposable mirror images of one another that rotate plane polarised light in opposite directions |
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When does optical isomerism show up in complex ions |
Octahedral complexes with 3 bidentate Ligands Eg. nikel bonded to three ethane 1,2 di amine Ligands |
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When does Cis and trans isomerism show up in complex ions |
1) square planar complexes when 2 pairs of Ligands When the two same Ligands are together they are cis when they are diagonal it’s trans Eg Ni(Cl)2(NH3)2 cisplatin and transplatin 2)on an octahedral complex when there are two of one kind of ligand and 4 of another .when the two are on opposite it’s trans when they are next to one another it’s via eg.Ni(CL)2(H20)4 |
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Why are transition metal complexes coloured |
The 3d orbitals of transition metals all have the same energy until they bonds to Ligands some orbitals get more energy than others. More electrons occupy the lower orbitals ,to jump up to orbitals at a higher energy level they need energy equal to the energy gap. They absorb some wavelengths of visible light to make up the energy gap. The other wavelengths are reflected these combine forming the colour that is seen
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Formula to work out energy gap |
H |
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What is haemaglobin |
Haemoglobin is a protein found in the blood that helps transport oxygen around the body . It’s a Fe2+ hexa co-ordinated with 4 pairs from nitrogen in a multidentate molecule called porphyn A fifth electron pair is from globin a protein the lady comes from a water or oxygen molecule It substitutes water for oxygen in high O2 conc eg. Lungs and it substitutes oxygen for water in low oxygen conc eg muscles . These places need it |
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Carbon monoxide poisoning can occur when |
1) Carbon monoxide is inhaled they can be substituted in for water . 2)Forming carboxy heamaglobin. But the bond carbon monoxide forms with Fe 2+ is very strong it therefore doesn’t readily substitute with water or oxygen. 3)So that molecule of haemoglobin is no useless . If this happens to many molecules the body cells are starved of oxygen. |
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Ligand exchange reactions can be easily reversed unless |
The new complex ion is much more stable than the old one , if the new Ligands for stronger bonds to the central metal ion its harder to reverse |
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.Why is it hard to reverse a ligand exchange reaction involving mono and then multidentate Ligands |
Multidentate Ligands form more stable complexes then monodentate Ligands |
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Enthalpy change in ligand exchange reactions |
When a ligand exchange reaction occurs the bonds that are broken and the new ones formed are usually very similar in strength thus low enthalpy |
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Entropy change when multidentate Ligands substitute in for monodentate ligands |
The entropy in the system increases as there are more particles . So complexes with multidentate Ligands are more stable then Ligands with monodentate Ligands this is the chelate effect. Eg when 6 NH3 Ligands in [Cr(NH3)6] Are substituted for EDTA (forms 6 co-ordinate bonds) it’s hard to reverse because the reverse causes a decrease in entropy |
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Five oxidation states of vanadium and colours |
1) +5 / VO2+ / yellow 2)+4/ VO2+/blue 3)+3/V3+/green 4)+2/V2+/ violet |
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Vanadium can be reduced by adding it to |
Zinc metal in an acidic solution 1)2VO2+ + Zn + 4H+ —> 2VO2+ + zn2+ + 2H2O Yellow to blue 2) 1)2VO2+ + Zn + 4H+ —> 2V3+ + zn2+ + 2H2O Blue to green 3)2V3+ +Zn —>2V2+ + Zn2+ Green to violet |
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What do redox potentials of an ion / atom tell you |
1) how easily it’s reduced 2)it’s the same as an electrode potential 3) the more positive the less stable therefore the more likely to be reduced 4)measured at standard conditions (1mol dm3 all reactants and standard hydrogen electrode) |
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How does PH effect redox potentials |
Some need H+ to be reduced so in acidic conditions would be reduced more easily Some release OH - so equilibrium favours this in acidic conditions In general redox potentials will be more positive in low PH as ion is more easily reduced |
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So why isn’t zinc / scandium compounds coloured |
There are no electrons or it’s full in 3d sub level so electrons can’t move up and therefore don’t absorb wavelengths of light to do so. |
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Rollins reagent |
Ag + is reduced to silver Ag by aldehydes and the silver precipitate forms the mirror on the test tube . Ketones don’t reduce it have no reaction eg RCHO+2[Ag(NH3)2]+ OH- —> RCOO- + 2Ag + 4NH3 + 2H2O |
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Three things that can alter the energy gap |
1) number of Ligands eg. Small H20 6 can fit around Cu but only 4 large Cl can . 2)type of Ligands 3) change in co-ordination number (always results in a change of ligand type ) |
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Enthalpy change in ligand exchange reactions |
When a ligand exchange reaction occurs the bonds that are broken and the new ones formed are usually very similar in strength thus low enthalpy |
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What is spectroscopy |
The study of what happens when radiation interacts with matter |
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How can spectroscope be used to determine the concentration of a solution |
Measuring how much light it absorbs . White light is shone through a filter which only allows the colour of light that the sample absorbs through to the sample . On the other side of the sample there is a colorimeter which shows how much of this light was absorbed by the sample . The more concentrated a sample the more light it will absorb. |
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What is ligand subtitution |
ligand substitution involves the exchange of one ligand for another |
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Substitution of similarly sized ligands |
When you substitute a ligand with another of a similar size eg.NH3 with H2O there is no change in co ordination number as they form the same number of co ordinary bonds. But there is a colour change as the EA changes |
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When you substitute different sized Ligands |
If Ligands are different sizes eg Cl- is larger than H2O and NH3 fewer Cl- can fit affluent the metal ion .There is a change in the co-ordination number and thus shape |
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Partial substitution of Ligands |
You can have some of the Ligands substituted but not others eg. [Cu(H2O)6]+4NH3–> [cu(NH3)4(H2O)2]+4H2O |
