d Block

Why can d-block elements form more than one type of ion

successive ionisation energies for the transition elements tend to increase gradually without large jumps in value

3d and 4s electron energy levels are very similar in energy

Energies of the d-orbitals are very similar

Define a transition metal

have either a partly filled 3d sub shell of form ions that have a partly filled 3d sub-shell

Why are most compounds that contain elements in high oxidation numbers referred to as complexes

If these ions were to form ionic compounds they would have a very high charge density

It would require too much energy to remove the 4,5,6,or 7 electrons to create the ion

Define ligand

A species possessing a lone pair of electrons which can form a co-oordinate bond to a central metal ion.

How can [CoCl4]^2- be used as a test for water

it is a blue compound that turns pink in contact with water. It forms [Co(H₂O)₆]²⁺

Name the kind of reaction on the previous flashcard

ligand exchange

What complexes have a coordination number of 4

tetrahedral

What complexes have a coordination number of 6

octahedral

What name does an atom or group of atoms have if it only forms one coordinate bond

monodentate ligand

Name of molecules that can form two coordinate bonds

bidentate ligands

Name of molecules that can form several coordinate bonds

polydentate ligand

What happens if HCl is added to [Cu(H₂O)₆]²⁺

[CuCl₄]²⁻ + H2O is made. This is an equilibrium reaction.

[Cu(H₂O)₆]²⁺(aq) + 4Cl⁻(aq) ⇌ [CuCl₄]²⁻(aq) + 6H₂O(l)

Colour change of this equilibrium if HCl is added

[Cu(H₂O)₆]²⁺(aq) + 4Cl⁻(aq) ⇌ [CuCl₄]²⁻(aq) + 6H₂O(l)

Bright blue to yellow-green

Cr³⁺

green

Cr₂O₇^2-

orange

Fe²⁺

Pale green

Co²⁺

pink

CrO₄^2-

yellow

MnO₄^-

purple

Fe³⁺

Red-brown

Cu²⁺

Pale blue

How are transition metals coloured

The presence of ligands around the central metal ion causes the d-orbitals to split into two energy levels.

The lower energy level contains three d-orbitals and the higher energy level contains two d-orbitals

When visible light is passed through a solution of this ion, some of the energy is absorbed which promotes an electron to a higher 3d orbital.

When light of a particular colour is absorbed, its complementary colour is reflected.

Why is Cu⁺ not coloured

Copper(I) complexes have an electronic configuration with a full d sub-shell

Why is Sc³⁺ ions not coloured

Sc³⁺ ions have an empty d sub-shell, meaning that electrons cannot move from lower to higher orbitals.

Equation when hydroxide ions are added to Cr³⁺

Cr³⁺(aq) + 3OH^-(aq) ⇒ Cr(OH)3(s)

Observations for this reaction

Cr³⁺(aq) + 3OH^-(aq) ⇒ Cr(OH)3(s)

green solution to grey green precipitate

Observations when OH- is added to Fe²⁺

Pale green solution to Dark green precipitate

Observations when OH- is added to Fe³⁺

Yellow solution to Red-brown precipitate

Observations when OH- is added to Cu²⁺

Pale blue solution to Pale blue precipitate

Observations when excess OH- is added to Fe²⁺

no further change

Observations when excess OH- is added to Cr³⁺

grey green precipitate dissolves giving a deep green solution

Equation when excess OH- is added to Cr³⁺

Cr(OH)3​(s)+3OH−(aq)→[Cr(OH)6​]3−(aq)

Observations when excess OH- is added to Fe³⁺

No further change

Observations when excess OH- is added to Cu²⁺

No further change

What happens if ammonia solution is added to [Cu(H₂O)₆]²⁺

[Cu(NH₃)₄(H₂O)₂]²⁺ + H2O

Shape of [Cu(NH₃)₄(H₂O)₂]²⁺.

Heterogenous

catalysts are in a different physical state to the reactants.

Homogenous

catalysts are in the same physical state as the reactants.

Define catalyst

substances that increase the rate of a chemical reaction by providing an alternative pathway with a lower activation energy

[Fe(H₂O)₆]²⁺

Pale green

[Fe(H₂O)₆]³⁺

Yellow

Catalyst for production of nitric acid

Platinum heterogenous

Catalyst for hydrogenation

Nickel heterogenous

Catalyst for polymerisation of Ethene

TiCl3 or TiCl4 - Ziegler-Natta catalysts

Catalyst for contact process

Vanadium oxide V2O5 heterogenous

Catalsyst for haber process

Fe heterogenous catalyst

Explain why both iron and copper are classed as transition elements, whilst zinc is not.

Iron and copper have partially filled d-orbitals in their ions, zinc does not