Transition elements Flashcards
Define a transition element
A d-block element which forms at least one ion with a partially filled d sub-shell
What are the 2 elements that are not considered transition elements and why?
Scandium and zinc- they do not form ions with partially filled d sub-shells, however they are still d block elements as the last electron goes into a d sub-shell
What are 3 properties of transition elements?
-They can act as industrial catalysts (e.g. iron in the Haber process to make ammonia)
-They form coloured compounds
-They form compounds with different oxidation states
What is the noble gas configuration of chromium?
[Ar]4s13d5
What is the noble gas configuration of copper?
[Ar]4s13d10
Which electrons do transition elements lose first when forming ions?
4s
Define ligand
A species with a lone pair of electrons which it can donate to a metal ion to form a co-ordinate bond in a complex ion
Define complex ion
A central metal ion surrounded by ligands which have formed co-ordinate bonds to the metal
Define co-ordination number
The number of co-ordinate bonds formed by ligands to the central metal ion
Define bidentate ligand
A ligand which donates 2 pairs of electrons to a metal ion, forming 2 co-ordinate bonds
What shape is formed when there are 4 large ligands (e.g. chloride ions) around a central metal ion? What is the bond angle?
Tetrahedral, 109.5 degrees (or sometimes square planar, 90 degrees)
What shape is formed when there are 6 small ligands (e.g. water or ammonia) around a central metal ion? What is the bond angle?
Octahedral, 90 degrees
What is cis-platin?
This is an anti-cancer drug, existing as 2 stereoisomers cis and trans, in a square planar arrangement. It prevents DNA replication in cancer cells by a ligand replacement reaction with DNA. Effective for treating cancer, however is still toxic to healthy cells. Transplatin however is toxic.
Transition metal ions + alkali —-> ?
Metal hydroxide (as precipitate)
What does a reducing agent do?
Reduces other species but is oxidised itself
What does an oxidising agent do?
Oxidises other species but is reduced itself
What are the steps you should follow to write half equations?
1) Oxidation or reduction?
2) How many electrons lost or gained?
3) Put electrons on correct side
4) Balance O using H2O
5) Balance H2O with H+
6) Balance charges and atoms
What is the ratio for MnO4- and Fe2+
1:5
Why can HCL not be used for a potassium manganate titration?
It would oxidise Cl- to Cl2, so would affect the volume of KMnO4 required
Why can ethanoic acid not be used in a potassium manganate titration?
It is a weak acid so wouldn’t provide enough H+ ions
Why can concentrated H2SO4 or HNO3 not be used in a potassium manganate titration?
They are oxidising agents themselves so affect volume of KMnO4 required
What acid is used in excess in the potassium manganate titration and why?
Dilute H2SO4 to prevent the reducing agent from oxidising
What is the ratio for MnO4- and C2O4-
2:5
What colour does the solution go in a iodine-thiosulfate titration?
Brown, then the precipitate is off-white. Once starch is added, it turns deep blue. The end point is when this fades.
What colour is the end point in the potassium manganate titration?
Pale pink
What is the ratio for Cu2+ and sodium thiosulfate?
2:2 (divide by 2 to find I- moles)
