Transition metals Flashcards
TM & d block elements?
all TM are d block elements but not all d block elements are TM
d block elements with a strange electron arrrangement?
Cr and Cu
Cr electron arrangement ?
[Ar]4s13d5 - electron moves from 4s to 3d orbital
Cu electron arrangement?
[Ar] 4s13d10
Why does Cr have this arrangement?
• repulsion between the 2 4s e- causes e- to move to empty 3d subshell
Why does Cu have this arrangement?
e- moves from 4s orbital to 3d, making 3d subshell full which makes Cu more stable
when d block elements form ions which electrons are lost?
4s lost first bc they’re the outer shell electrons
first row d block elements that are not TM?
Scandium and zinc
what is a TM?
element that forms at least 1 ion w a partially filled d subshell
Sc ion always has an ox no of
+3
Zn ion always has an ox number of
+2
Why is the most common ox state for TM +2?
2 4s e- lost
Cu (s) colour?
red/ brown solid
KMnO4 colour and use?
- potassium manganate (VII)
- purple
- redox titrations
CuSO4 colour and use?
- blue
- crystal growing
- testing for amines
Na2Cr2O7 colour and use?
- orange
* oxidation of primary and secondary alcohols
AgNO3 colour and use?
- colourless
* testing for halide ions
FeBr3 colour and use?
- yellow
* halogen carrier
TM general?
- exist in >1 oxidation state
- form coloured ions
- act as catalysts
BZ y axis?
no. of particles
Ni as a catalyst?
- heterogeneous
- hydrogenation of alkenes
- producing margarine
MnO2 as a catalyst?
- heterogeneous
* decomposition of H2O2 into H2O and O2
Fe as a catalyst?
- hetero
- haber process
- producing NH3
Vanadium pentoxide, V2O5 as a catalyst?
- hetero
- contact process - SO2 + 1/2O2 ➡ SO3
- producing sulphuric acid
Cu as a catalyst?
- hetero
- oxidation of ethanol to form ethanal
- CH3CH2OH ➡ CH3CHO + 2H+ + 2e-
- Cu2+ + 2e- ➡ Cu(s)
unusual for het to be
redox
Co2+ as catalyst?
- homogeneous
- sodium potassium tartrate and H2O2
- produces CO2
Fe2+ as a catalyst?
- homogeneous catalyst
- iodide and peroxodisulphate ions
- produces iodine
Heterogenous catalysis
1) Adsorption - reactants form weak bonds to catalyst - O bonds w catalyst by donating lone pair of e-
2) weakens bonds within H2O2 + other bonds form - reaction occurs. Reaction takes place on surface of catalyst
• lower Ea bc reactants held in correction orientation for reaction or weaker bonds
3) desorption - bonds between catalyst and product break. Product leaves catalyst surface and catalyst can b resued
heterogeneous catalysis is when
- catalyst and reactants in diff states
* TM can act as het catalysts bc empty d orbitals so can accept LP of e-
TM have a vacant ?
d orbitals so lone pairs can be donated to the TM
TM form
gelatinous precipitates
homogeneous catalysis?
TM can easily change ox state - can exist in diff oxidation states
Homogeneous catalysis equations?
- break equation down into oxidation and reduction equations
- oxidise/ reduce catalyst
- if O, goes w reduction equation
- do the opp
- pair again
what other impact could a catalyst have?
• w a catalyst, may have a higher cell potential than uncatalysed, more likely to occur
molecular ion?
ion w covalent bond inside, is charged
dative covalent bond?
lone pair is donated by 1 atom - lone pair needed and empty orbital needed
Complex ions involve
DCB and ligands
ligands?
- have a LP of electrons, which they donate to form dative covalent bonds to TM ions. This is then known as a complex ion
- can be neutral or an anion - negatively charged ion
lone pairs in ligand determines?
how many bonds ligands can form
bidentate ligands have ? lone pairs
2
e.g. of hexadentate ligand?
EDTA4-
what is the co-ordination number?
number of dative covalent bonds to TM ion. CN usually 6, octahedral shape
when is the CN 4?
- When halide ions are the ligand, tetrahedral shape
* G10 metals, square planar shape
when is the CN 2?
- Ag
* Linear
ligand substitution?
a ligand in a complex ion can be substituted by another ligand. The replacement ligand forms a more stable complex ion
monodentate is the ?
easiest to remove in substitution. Hexadentate are the hardest bc wraps itself around TM
when forming precipitate?
can use ion(aq) but when forming complex ion must write as [ion(water)6}charge
same result after adding few drops NaOH and ?
a few drops of aq ammonia - prec forms
only ? changes when excess NaOH is added?
Cr3+. Green solution forms, precipitate dissolves
why do precipitates disappear when acid is added?
bases so react w acid to form, salt and water
Cr3+ reaction?
- when NaOH added: green gel prep forms
- excess: clear green solution - [Cr(OH)6]3- forms
- w acid: reaction reversed - Cr(OH)3 forms
darkening on surface is due to
oxidation
Homogeneous catalysis?
• in solution
