3.4 D block Flashcards
Define D block element
have their outer most electron in a full or partly full d orbital
Define transition metal
have atoms or ions with a partly filled d d orbital
properties of transition metals
- variable ox state
- form coloured compounds
- can react to form complex ions
- act as catalysts
VCCC
Discuss variable oxidation state
transition metals have partly filled d orbitals which easily loose or gain electrons (because they require small amounts of energy) which results in more than 1 ox state.
What is a catalyst and what are the two types?
- substance which speeds up the rate of a reaction without being used up providing an alternative route lowering the activation energy.
- homogenous- same phase as reactants
- heterogenous- diff phase as reactants
example of catalyst:
1) heterogenous
iron (Fe) in haber process N2 + 3H2 -> 2NH3
example of catalyst:
2) heterogenous
nickel in hydrogenation of alkenes to alkanes
example of catalyst:
3) heterogenous
MnO2 in decomposition of h2o2
example of catalyst:
4) homogenous
V2o5 vanadium oxide in contact process
2s202 + o2 -> 2so3
modes of catalyst: heterogenous
reactants adsorb onto to surface of a transition metal which allows and increase in collisions between reactants and the products deadsorp from the surface of the metal
modes of catalyst: homogenous
work by transition metals changing ox state and allowing reaction to proceed with a lower ea
How do catalysts work?
a) cuz tm have partly filled d orbitals they can accept/ release extra electrons e.g mno4- to mn2+
b) also cuz they have partly filled d orbitals they have spaces to act as docking stations for gas reactants to bind to and are held long enough for a reaction to happen and pop off as a new product.
Define complex ion
when a tm ion binds using co-ordinate bonds to one or more ligands
structure of complex ion
[ Cu(H20)6 ] 2+
ligand- brackets inside of square brackets
central tm ion- Cu
Define ligand
a molecule or ion with a lone pair of electrons that form co-ordinate bonds with a tm ion which has a partially filled d orbital.
Define co-ordination number
number of ligands that bond to a central tm ion
How are coloured complexes formed?
- partially filled d orbitals arrange so that 3 are at lower energy than the other two
- there will be energy available for an electron to be promoted from lower to higher energy level but in doing so energy adsorbed from white light and remaining wavelengths reflect to give colour .
colour changes with:
metal ion
ox state of ion
ligand bonded
