Developing metals - Unit 9 Flashcards
Transition metals?
Metal that can form more than one stable ion with a partially full d-orbital
When writing an e- configuration, does D go before S
Yes
Anomalies for e- configuration of D-block metals + why?
Cr = (Ar) 3d(5) 4s(1) Cu = (Ar) 3d(10) 4 s (1)
less repulsion if e- are places singly in d-orbitals than if they were paired together in the s-orbital
e- configuration of Ar
1s(2)2s(2)2p(6)3s(2)3p(6)
How do the d-block metals differ?
As you go across each element has 1 more e- in the 3d sub shell
Rule to remember when writing e- configerations?
Put numbers in correct order
Rule to remember when drawing the e- configuration of ions of the d-block
4s shell loses e- first
e- configuration of Cr(3+)
(Ar) 3d(3)
Are Zn + Sc transition metals +why?
No
- Sc only forms 3+ ion (behaves like group 3 metal) with no d-orbital
- Zn only forms 2+ ion (behaves like group 2 metal) with full d-orbital
Why do transition metals have many oxidation states?
there’s a number of stable arrangements of d + s block e-
Overall equation for redox titration using potassium manganate?
5Fe(2+) + MnO4(-) + 8H(+) –> 5Fe(3+) + Mn(2+) + 4H2O
When is the end point of the titration?
When there’s a pink colour (when MnO4- in excess)
Purpose of redox titration?
find conc. Fe2+ ions
colour potassium manganate?
KMnO4(-) = purple
Features transition metals?
1 - Form coloured compounds
2 - Have variable oxidation states
3 - Are catalysts
4 - Form complex ions
colour Fe2+ vs Fe3+ ions in sol.
Fe2+ = green
Fe3+ brown
Colour V2+, V3+, V4+, V5+ in sol.
V2+ = lilac V3+ = green V4+ = blue V5+ = yellow
How do transition metals act as catalysts?
- They have variable oxidation states
- They have vacant d -orbitals
- Therefore can accept e- to from dative covalent bonds
Heterogeneous catalysis of transition metals?
1 - use e- in partially full d orbital to form weak bonds to reactants on metal surface
2 - once the reaction has occurred, the bonds break releasing products
Homogeneous catalysis of transition metals?
1 - transition metal forms intermediate compound with reactant
2 - intermediate breaks down to form product
why are transition metals effective catalysts in redox reactions?
1 - They can move from one oxidation state to another
states in heterogenous catalyst transition metals?
Transition metal - solid
Reactant - gas/liquid
states in homogenous catalyst transition metals?
both in aqueous
What are the things that control the splitting of d-orbitals?
1 - The metal
2 - It’s Oxidation state
3 - Number and type ligand
4 - Shape of complex
Colorimetry?
1 - Zero with a distilled water
Colour of Fe(2+) , Fe (3+), Cu+, Cu(2+) in aq sol.
- Fe (2+) = green
- Fe (3+) = orange/brown
- (Cu (+) = no colour - unstable in aq sol.
- Cu (2+) = blue
Why do are trasiiton metal complexex coloured?
1 - Ligands cause d-orbital splits so some d-orbitals higher in E than others
2 - This creates smaller E gap
3 - Therefore allows e
- to absorb lower freq. light in visible region
4 - therefore, e- moves to higher e level, emitting light
What ia a bidentet liagand?
Soemthing that can form 2 dative covalent bonds to a metal ion
What is a bidentate ligand?
Something that can form 2 dative covalent bonds to a metal ion
monodentate
Something that can form 1 dative covalent bonds to a metal ion
What does the colour of a trnsiiton metal complex depend on?
1 - no. d-orbital e - ion metal ion
2 - arrangemnt liganda affects plittign d orbital
3 - nature of ligand
4 - no. ligands
potential difference?
A measure of how much electrode is tending to release or accept e-
purpose salt bridge?
the ions carry the contact so there is an electrical current but the two solutions don’t mix
conditions for electrochemical cell?
298 k
1 moldm-3
Why is Pt electrode used?
Unreactive
When is Pt used?
When half equations doesn’t involve metal but ions e.g Fe3+ + e- –> Fe(2+)
What does it mean if E cell is pos vs neg?
\+ = reaction feasible - = reaction can't occur at standard cond.
If E cell is pos why my the reaction still not occur?
- only tells you whether reaction is possible
- not rate
- therefore in reality reaction may be so slow that no change is observed
Why could you do if E cell neg?
change conditions as this will change pd values
Why Fe rusts?
When it rusts it forms layer Fe2O3xH200
This is no protective
Therefore layers beneath also corrode
equation for rusting Fe?
Fe2+ + 2e- –> Fe
1/2 O2 + H2O + 2e- –> 2OH-
1/2 O2 + Fe + H2O –> Fe2+ + 2OH-
Fe2+ + 2OH- –> Fe (OH)2
+ O2(aq)
Fe2O3.xh20
Sacrificial protection
- More electroneg metal is oxidised
- shifts it’s equilibrium to left
- Therefore fe equilibrium shifts to right, preventing prod Fe2+
Protecting against rust?
1 - layer paint, plastic film
2 - protective Zinc oxide layer. even if scratched Fe not rusted as Zinc more electronegative
3 - Supply e- to the metal from electrical source
4 - connect neg terminal battery to metal, therefore cathode. e- flow anode –> cathode
Why Al, Zn, and Cr don’t rust?
form protective oxide layer
What is a complex?
- pos metal atom/ion surrounded by neg ions with lone pair e-, ligands
Bonds in complex?
- e- pair from ligand shared with metal ion forming datice covalnet bonds
Coordination no.?
no. dative covalent bonds between ligand and central ion.
shape complexes with coordination no. 6, 4,2?
6 - octahedral
4 - tetrahedral / square planar
2 - linear
How can complexes have irregular shapes?
If bonding between betwen some ligands and cnetral ion more strogn than othere
Polydente ligands?
ligands that can bdond more than once to a metal ion through more than one atom
Example of ligand substitution?
1 - conc. HCl + (Cu(H2O)6)2+ (aq)
2 - Cl- displace water ligands
3 - (CuCl4))2-
4 - blue –> yellow
1 - conc. NH3(aq) + (Cu(H2O)6)2+ (aq)
2 - NH3 dispale water logands
3 - (Cu(NH3)4(H2O)2)2+ + 4H2O
When does ligand substitution occur?
If teh new complex more stabel than the pervious complex
What does the stabiloty of a complex depend on?
It’s ligands
