5.3 Transition Metals
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- Created by: elbungay1
- Created on: 27-03-19 16:39
What is a transition element?
A d-block element that has an incomplete d-sub-shell as a stable ion
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Why are scandium and zinc not transition metals?
Scandium forms only the Sc3+ ion, in which the d-orbitals are empty. Zinc forms only the Zn2+ ion, in which the d-orbitals are full
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What are the physical properties of transition elements?
High densities, melting points and boiling points. When solid, exist as giant metallic lattice containing delocalised electrons which move freely to conduct electricity
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What are the chemical properties of transition elements?
Variable oxidation states, undergo disproportionation reactions, form coloured compounds, can act as catalysts
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Give examples of transition metals as catalysts in industry
Iron metal is the catalyst in the Haber process, formation of ammonia. Nickel is the catalyst for the hydrogenation of alkenes.
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What is a ligand?
A molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond
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What is a complex ion?
A transition metal ion bonded to one or more ligands by coordinate bonds
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What is the coordination number of a complex ion?
The total number of coordinate bonds formed between a central metal ion and its ligands
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What is EDTA?
A multidentate ligand that can form 6 coordinate bonds. It is a chelating agent, decreases concentration of metal ions in solution by binding to them into a complex.
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What is the shape of complex ions with six-fold coordination?
Octahedral, bond angles of 90° or 180°
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What is the shape of complex ions with four-fold coordination?
Form tetrahedral shape usually. Cis-platin forms square planar
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Describe how cis-trans isomerism can occur in Complex ions
Four monodentate ligands and 2 different monodentate ligands, Cis when two are 90°, trans when 180°. Or with two bidentate ligands and two monodentate ligands.
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What is the drug cis-platin used against and how does it function?
Basis for modern chemotherapy. Binds to DNA of fast-growing cancer cells preventing cell division and tumour growth. Has bad side effects of severe sickness, hair loss and fatigue
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Describe how optical isomerism occurs in complex ions
Requires: 3 bidentate ligands, two bidentate and two monodentate, complex with hexadentate. can form non-superimposible mirror images of each other
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Describe the Ligand substiution reaction between aqueous copper(ii) ions and ammonia
[Cu(H2O)6]2+ + 4NH3 (equilibria) [Cu(NH3)4(H2O)2]2+ + 4H2O. Pale blue solution initially forms pale blue precipiate of Cu(OH)2 which redissolves to form deep blue solution. H2O bonds longer forming distorted octahedral shape
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Describe the ligand substitution between copper(ii) ions and hydrochloric acid
[Cu(H2O)6]2+ +4Cl- (equilibria) [CuCl4]2- + 6H2O. Pale blue solution forms yellow solution. Chlorine ligands bigger so forms tetrahedral shape
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Describe the ligand substitution reaction between Chromium(III) and ammonia
[Cr(H2O)6]3+ + 6NH3 (equilibria) [Cr(NH3)6]3+ + 6H2O. Grey-green solution initially forms green precipitate of [Cr(H2O)3(OH)3]. This redissolves to form dark green solution.
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Describe the structure of Haemoglobin complex ion
Four coordinate bonds between Fe2+ ionsand the nitrogen ions in haem structure. One further coordination bond to protein globin. A final coordinate bond can form to an oxygen molecule which is transported
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What effects does Carbon Monoxide have on transport of Oxygen?
CO bonds more strongly to haemoglobin than oxygen, less haemoglobin left to bind to oxygen molecules. Reaction is not reversible, once on a haem group, CO cannot be removed and haemoglobin cannot do its function of transporting oxygen.
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Describe the colours of different transition metal ion precipitates in NaOH
Cu(II) pale blue. Fe(II) green, rusty brown when exposed to air. Fe(III) rusty brown. Mn(II) brown. Cr(III) green
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Describe a test for the Ammonium Ion
Reacts with hydroxide ion to produce ammonium gas and water. Distinctive smelling gas, turns damp red litmus paper blue
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Describe a test for Carbonate ions
React with acids to produce effervescence as CO2 is produced, which will turn limewater milky.
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Describe a test for the sulfate ion
React with barium ions to form insoluble salt Barium Sulfate, white precipitate
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Describe a Test for Cu2+ ions
Blue solution and a blue precipitate in OH- or NH3. In excess NH3 the precipitate re-dissolves to provide a blue solution. There's no change in excess OH-
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Describe a Test for Fe2+ ions
Green solution that forms a green precipitate in NH3 or OH-. No change in excess NH3 or OH-
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Describe a Test for Mn2+ ions
Pink solution that forms a brown precipiate in NH3/OH-. No change in excess NH3 or OH-
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Describe a Test for Cr3+ ions
Violet solution that forms a green precipitate in NH3/OH-. In excess NH3, precipitate dissolves to form purple solution. In excess OH-, precipitate dissolves to form a green solution.
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Describe a Test for Fe3+
Yellow/brown solution that forms a brown precipitate in NH3/OH-. No change in excess NH3 or OH-
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Other cards in this set
Card 2
Front
Why are scandium and zinc not transition metals?
Back
Scandium forms only the Sc3+ ion, in which the d-orbitals are empty. Zinc forms only the Zn2+ ion, in which the d-orbitals are full
Card 3
Front
What are the physical properties of transition elements?
Back
Card 4
Front
What are the chemical properties of transition elements?
Back
Card 5
Front
Give examples of transition metals as catalysts in industry
Back
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