Transition elements

Question 1

What is a transition element?

Answer 1

A d-block element that forms at least one ion with an incomplete d sub-shell.

Question 2

Which block of the periodic table contains the transition elements?

Answer 2

The d-block.

Question 3

Name one element that is in the d-block but not a transition metal.

Answer 3

Scandium or Zinc.

Question 4

Why is Scandium not considered a transition metal?

Answer 4

Sc3+ has an empty d-orbital, so no partially filled d sub-shell.

Question 5

Why is Zinc not considered a transition metal?

Answer 5

Zn2+ has a full d-orbital (3d10), so no partially filled d sub-shell.

Question 6

State three properties typical of transition metals.

Answer 6

Variable oxidation states, coloured compounds, catalytic activity.

Question 7

What causes the variable oxidation states in transition metals?

Answer 7

The similar energy of 3d and 4s orbitals allows for different numbers of electrons to be lost.

Question 8

What is a ligand?

Answer 8

An ion or molecule that donates a lone pair of electrons to a central metal ion.

Question 9

What is a complex ion?

Answer 9

A central metal ion bonded to ligands via coordinate bonds.

Question 10

What is the coordination number of a complex?

Answer 10

The number of coordinate bonds to the central metal ion.

Question 11

What shape is a complex with a coordination number of 6?

Answer 11

Octahedral.

Question 12

What shape is a complex with a coordination number of 4?

Answer 12

Tetrahedral or square planar.

Question 13

Give an example of a bidentate ligand.

Answer 13

Ethanedioate (C2O4^2-) or 1,2-diaminoethane (en).

Question 14

What is a chelate?

Answer 14

A complex with a multidentate ligand forming a ring structure.

Question 15

What is a ligand substitution reaction?

Answer 15

When one ligand is replaced by another in a complex.

Question 16

What is a precipitation reaction in transition metal chemistry?

Answer 16

A solid metal hydroxide forms when NaOH is added to a metal ion solution.

Question 17

What is a redox reaction in transition metal chemistry?

Answer 17

An electron is transferred, changing the oxidation state of the metal.

Question 18

Colour of [Cu(H2O)6]2+ (aq)

Answer 18

Pale blue.

Question 19

What happens when you add ammonia to [Cu(H2O)6]2+?

Answer 19

Forms deep blue solution [Cu(NH3)4(H2O)2]2+.

Question 20

What happens when you add chloride ions to [Cu(H2O)6]2+?

Answer 20

Forms yellow solution [CuCl4]2-.

Question 21

What colour precipitate forms when NaOH is added to Fe2+ solution?

Answer 21

Green precipitate of Fe(OH)2.

Question 22

What colour change indicates the oxidation of Fe2+ to Fe3+?

Answer 22

Green to orange-brown indicates Fe2+ oxidised to Fe3+.

Question 23

Why do transition metal complexes show colour?

Answer 23

d-electrons absorb energy and jump between split d-orbitals, transmitting visible light.

Question 24

How does a colorimeter help analyse transition metals?

Answer 24

It measures absorbance of light at specific wavelengths to find concentration.

Question 25

Give an example of a transition metal used as a catalyst.

Answer 25

V2O5 in the Contact Process or Fe in the Haber Process.

Question 26

Why do transition metals make good catalysts?

Answer 26

They provide a surface or change oxidation states to lower activation energy.

Question 27

What is a ligand in transition metal chemistry?

Answer 27

A molecule or ion that donates a lone pair to a metal ion, forming a coordinate bond.

Question 28

Give examples of monodentate and bidentate ligands.

Answer 28

Monodentate: H2O, Cl⁻, NH3. Bidentate: NH2CH2CH2NH2 (en).

Question 29

What is a complex ion?

Answer 29

A central metal ion bonded to ligands via coordinate bonds.

Question 30

What is a coordination number?

Answer 30

The number of coordinate bonds formed with the central metal ion.

Question 31

Give examples of six-fold and four-fold coordination.

Answer 31

Six-fold: [Cu(H2O)6]²⁺, [Fe(H2O)6]³⁺. Four-fold: [CuCl4]²⁻, [CoCl4]²⁻.

Question 32

What type of stereoisomerism is shown by Pt(NH3)2Cl2?

Answer 32

Cis-trans isomerism.

Question 33

What is an example of a complex showing optical isomerism?

Answer 33

[Ni(NH2CH2CH2NH2)3]²⁺ shows optical isomerism.

Question 34

What is the function of cisplatin in medicine?

Answer 34

Used as an anti-cancer drug by binding to DNA and preventing cell division.

Question 35

What happens in ligand substitution between [Cu(H2O)6]²⁺ and NH3?

Answer 35

Forms [Cu(NH3)4(H2O)2]²⁺, changing colour from pale blue to deep blue.

Question 36

What happens in ligand substitution from [Cr(H2O)6]³⁺ to [Cr(NH3)6]³⁺?

Answer 36

Ligands swap and solution colour changes from violet to purple.

Question 37

What is the role of iron in haemoglobin?

Answer 37

Fe²⁺ binds to O2 and CO via ligand substitution for oxygen transport and toxicity.

Question 38

What precipitate forms when NaOH is added to Cu²⁺?

Answer 38

Cu(OH)2, a pale blue precipitate.

Question 39

What happens with excess ammonia added to Cu²⁺?

Answer 39

Forms [Cu(NH3)4(H2O)2]²⁺, deep blue solution.

Question 40

What is the colour of Fe(OH)3 precipitate?

Answer 40

Orange-brown.

Question 41

What is the colour of Mn(OH)2 precipitate?

Answer 41

Light brown, darkens in air.

Question 42

What is the colour of Cr(OH)3 precipitate?

Answer 42

Green.

Question 43

What happens with excess NaOH to Cr(OH)3?

Answer 43

Forms [Cr(OH)6]³⁻, dark green solution.

Question 44

What happens with excess NH3 to Cr(OH)3?

Answer 44

Forms [Cr(NH3)6]³⁺, purple solution.

Question 45

What is the colour change when Fe²⁺ is oxidised to Fe³⁺?

Answer 45

Green to orange-brown.

Question 46

What is the colour change when Cr³⁺ is oxidised to Cr₂O₇²⁻?

Answer 46

Green to orange.

Question 47

What is the colour change when Cu²⁺ is reduced to Cu⁺?

Answer 47

Blue to white precipitate of Cu⁺.

Question 48

What happens during disproportionation of Cu⁺?

Answer 48

Forms Cu²⁺ (blue) and Cu (pink solid).

Question 49

What types of reactions might be expected from transition metal chemistry?

Answer 49

Ligand substitution, precipitation, and redox reactions.