Transition

What is a Transition Element

A d-block element that can form at least one stable ion that has a partially filled D subshell

What is a complex

A complex contains a central metal atom/ion dative bonded to 1 or more molecules/anions called ligands

What is a ligand

A molecule or ion that has at least 1 atom with a lone pair of e- which can be donated into a low-lying vacant orbital of a central metal atom/ion to form a dative bonded, forming a complex

Why Atomic Radii and 1st IE almost constant

1. No. of protons increase, nuclear charge increase

2. e- are added to inner 3d subshell and the 3d e- effectively shield 4s e- from nucleus

3. Increase in nuclear charge is insignificant

4. Electrostatic FOA btwn nucleus and valence e- barely increase

5. Atomic radii remain constant & Energy required to remove valence electrons increase very slightly

MP BP > s block elements

1. Both have TE n s block have giant metallic lattice structure held together by strong metallic bonds

2. Due to low energy level diff between 3d and 4s orbitals, TE can use 3d and 4s e- for sea of delocalised e-

3. s block can only use from s orbital

4. TE have stronger metallic bonding (electrostatic FOA between cations n sea of delocalised e- larger)

5. Higher mpbp

Density

1. Stronger metallic bonding → closer packing

2. Smaller atomic size

3. Higher mass

4. TE DENSER

Shape

Coordination no.

2 → linear

4 → tetrahedral or square planar

• only square planar can form cis trans

6 → octahedral

• can form cis trans

• cis is 90• apart, trans is 180• apart

pH

Generally acidic because

1. TM ion has high charge density → strongly polarising

2. Able to distort e- cloud of water molecules bonded to it, weakening O-H bonds and releasing H*

Cu²+ in water

[Cu(H2O)6]²+

Blue coloured solution

NH3 first added to Cu²+ (aq)

1. NH3 + H2O ⇌ NH4+ + OH-

2. [Cu(H20)6]^2+ + 2OH- ⇌ Cu(OH)2 + 6H2O

Form Cu(OH)2 → blue ppt

Excess NH3 added to Cu²+ (aq)

Ligand Exchange occurs forming deep blue solution

[Cu(H2O)6]²+ + 4NH3⇌ Cu(NH3)4(H2O)2]²+ + 4H2O

Does blue ppt dissolve

Yes

When excess NH3 added, [Cu(H2O)6]²+ is used up, shifting POE of formation of Cu(OH)2 left, dissolving blue ppt

How does d orbital split into 2 energy levels (octahedral)

1. In isolated gas phase, all partially filled 3d orbitals of metal ion are degenerate(same energy)

2. In octahedral complexes, energy of d subshell is larger than in gas-ion due to

3. Electronic repulsion btwn ligands’ lp and 3d e-

4. Energy of 3d x²-y² & z² > xy xz yz due to greater electronic repulsion due to ligands approaching central ion along axes

5. This results in d orbitals splitting into 2 energy levels

Why got colour

Continuing from prev explanation,

1. When d-e- from lower energy d orbital promotes to higher energy d orbital, it absorbs energy from visible light

2. Light energy not absorbed is reflected and seen as complex’s colour

Heterogeneous Catalyst (diff state)

Provides a surface where reactants are adsorbed and products are desorbed

1. Due to low energy diff between 3d n 4s orbital,

2. TE can use e- frm 3d n 4s for ready exchange of e- btwn catalyst n reactant molecules to form weak bonds

3. Adsorption weakens bonds in reactants molecules, lowering EA

Homogeneous (same state)

Works by its ability to exist in variable oxidation states

2 Step

Both steps involve interaction of opositely charged ions, attracting each other, speeding up rate of rxn

Why CO poisonous

1. CO acts as a monodentate ligand, donating its lp on C into vacant low-lying orbital in Fe(2) to form a dative bond

2. CO ligand much stronger than O2 ligand as it forms a much stronger dative bond to FE(2)

3. Very difficult for O2 to replace it

4. Rendering haemoglobin ineffective in transporting oxygen