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Topic 13.2

Topic 13.2. The d-block. d-block Elements & Tranisition Metals. TRANSITION METALS: Definitions, Characteristics, Identification Variable oxidation numbers Ligands Complexes Colours Catalytic actions & Contact, Haber processes. D-Block & Transtion Metals.

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Topic 13.2

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  1. Topic 13.2 The d-block

  2. d-block Elements & Tranisition Metals • TRANSITION METALS: • Definitions, Characteristics, Identification • Variable oxidation numbers • Ligands • Complexes • Colours • Catalytic actions & Contact, Haber processes

  3. D-Block & Transtion Metals • Transition metals are d-block metals, but not all d-block metals are transition! • Transition Metal: A d-block element that has a partially filled d-sublevel in one of its common oxidation states • Not transition: Sc and Zn • Draw electron configuration to explain:

  4. Properties • Hard, dense metals • First IE relatively constant due to e- shielding results in similar chemical and physical characteristics • Transition elements form coloured compounds and complex ions • Exist in a variable oxidation states (polyvalent) • Act as catalysts

  5. Variable Oxidation States • Oxidation state: the hypothetical charge on an atom if all bonds are ionic in nature • 4s and 3d shells are very close in energy; 4s e- lost first • Minimum oxidation state of +2 for transition metals (4s already removed) • Some form +3 or +4; highest stable is +7 having lost all bonding e- (Mn)

  6. Stability of oxidation state • To the right… the +2 is more stable due to high IE because of higher nuclear charge • To the left… the maximum oxidation state is more stable… lower IE because of lower nuclear charge: e- are more easily lost resulting in higher charge • The more stable the oxidation state, the weaker oxidizing agent it is, that is it’s less reactive • Common ones to memorize: Cr (+3, +6); Mn(+4,+7); Fe(+3); Cu(+1)

  7. Ligands • Neutral molecule or anion containing a non-bonding pair of electrons • These electrons can form dative(co-ordinate) covalent bonds with the metal ion to form complex ions. • Monodentate: only one spot where bond can be made to central atom • Usually octahedral with six ligands on central atom or tetrahedral with four ligands. This number of ligands is called co-ordination number.

  8. Ligand Forming Complex Ions

  9. Complex Ions • Complex ion: species with ligand bonded datively to central metal eg: [Cu(NH3)4]2+ • Dative bond: ligand provides both e- to be shared in covalent bond

  10. Complex Ions • Cationic or anionic • Some end up neutral (ligands and metal ion cancel) resulting in opposite of ionic behavior • Water soluble; conduct electricity in solution

  11. Common Complex Ions • Fe3+ + 6H2O → [Fe(H2O)6] 3+ • Fe3+ + 6CN → [Fe(CN)6] 3- • [Cu(H2O)6] 2+ + 4Cl- → [CuCl4]2-+6H2O • Ag+ +2NH3 →[Ag(NH3)2]+

  12. Colours of Ions • Charges around atom or ion affect d-orbital energies • Instead of same energy, two groups are formed because of symmetry. • Octahedral complex ions: 3 low E; 2 high E • Movement of electrons from low to high results in colour given off when light passed through exciting one e- to higher group • Energy difference corresponds to visible light frequencies

  13. Catalytic Activity • Catalyst: A substance that speeds up a chemical reaction by lowering the activation energy required for the reaction to take place. • Homogeneous most common (same state) • Transition metals are useful because: 1. Form complex ions with species that donate lone e- pairs; close contact 2. Variety of oxidation states – readily gain or lose e-

  14. Examples: • MnO2 decomposes hydrogen peroxide to water and oxygen • Contact Process: V2O5 producing sulfuric acid • Haber Process: Fe to make ammonia (NH3) • Fe in heme (part of haemoglobin carries O in blood) • Ni converting alkene to alkane • Co in Vitamin B12 (Important to production of red blood cells) • Pd and Pt in catalytic converter (automobiles exhaust systems reduce pollutants)

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