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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

Topic 13.2

The d-block

d block elements tranisition metals
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
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:
properties
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
variable oxidation states
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)
stability of oxidation state
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)
ligands
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.
complex ions
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
complex ions1
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
common complex ions
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]+
colours of ions
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
catalytic activity
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-

examples
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)