Module 5 Section 3 - Transition Elements

Question 1

When writing down the electronic configuration of a Period 4 d-block element, what must you consider?

Answer 1

The fact that 4s electrons fill up before 3d electrons (they’re lower in energy level)

Question 2

What is a transition element?

Answer 2

A d-block element that can form at least ONE STABLE ION with an INCOMPLETE d sub-shell

Question 3

When transition element ions are formed, which electrons are removed first?

Answer 3

The S ELECTRONS are removed first, then the d electrons

Question 4

State the electronic configuration of Fe, Fe2+ and Fe3+

Answer 4

Fe = 1s2 2s2 2p6 3s2 3p6 3d6 4s2
Fe2+ = 1s2 2s2 2p6 3s2 3p6 3d6
Fe3+ = 1s2 2s2 2p6 3s2 3p6 3d5

Question 5

Why is Scandium not a Tranisition Element?

Answer 5

Scandium only forms Sc3+ which has an EMPTY d sub-shell (remember the definition of a transition element)

Question 6

Why is Zinc not a Transition Element?

Answer 6

Zinc only forms Zn2+ which has a FULL d sub-shell (remember the definition of a transition element)

Question 7

Why do transition elements exist in variable oxidation states?

Answer 7

Because the energy levels of the 4s and 3d sub-shells are very close to one another.
So different numbers of electrons can be gained or lost using fairly similar amounts of energy.

Question 8

In terms of oxidation states, why can transition elements and their compounds make good catalysts?

Answer 8

Because they can change oxidation states by GAINING or LOSING electrons within their d-orbitals.
This means they can transfer electrons to speed up reactions.

Question 9

Why do Transition METALS make good catalysts?

Answer 9

Because they are good at adsorbing substances onto their surfaces to lower the activation energy of reactions

Question 10

Why are catalysts, like transition elements/metals, good for the industry and the environment?

Answer 10

They allow reactions to happen FASTER and at LOWER temperatures and pressures, reducing energy usage.

Question 11

Why can transition element catalysts pose health risks?

Answer 11

Many of the metals and their compounds are TOXIC, e.g. Copper can damage the liver and kidneys, manganese can cause psychiatric problems

Question 12

What happens when you mix a transition element ION with aqueous Sodium Hydroxide (NaOH) or aqueous Ammonia (NH3)?

Answer 12

You get a COLOURED HYDROXIDE PRECIPITATE

Question 13

What form do transition elements take in aqueous solutions?

Answer 13

[M(H₂O)₆]n+

if the metal is bonded to water, you may write it out as M^n+, but anything else = full formula

Question 14

Express the ionic equation for the reaction between aqueous Copper(II) ion and NaOH (OH-).

Answer 14

[Cu(H2O)6]2+ (aq) + 2OH- (aq) → [Cu(OH)2(H2O)4] (s) + 2H2O (l)

This can also be written as: Cu2+ (aq) + 2OH- (aq) → Cu(OH)2 (s)

Question 15

Express the ionic equation for the reaction between aqueous Copper(II) ion and NH3.

Answer 15

[Cu(H2O)6]2+ (aq) + 2NH3 (aq) → [Cu(OH)2(H2O)4] (s) + 2NH4+ (aq)

Question 16

What is the colour change when Copper(II) ion reacts to form a coloured hydroxide precipitate?

Answer 16

PALE BLUE solution → BLUE Precipitate

excess NH3; [Cu(OH)2(H2O)4] reacts further to form [Cu(NH3)4(H2O)2]2+ which is a DARK BLUE colour

Question 17

Express the ionic equation for the reaction between aqueous Iron(II) ion and NaOH (OH-).

Answer 17

[Fe(H2O)6]2+(aq) + 2OH-(aq) → Fe(OH)2(H2O)4 + 2H2O(l)

Question 18

Express the ionic equation for the reaction between aqueous Iron(II) ion and NH3.

Answer 18

[Fe(H2O)6]2+(aq) + 2NH3(aq) → Fe(OH)2(H2O)4 + 2NH4+ (aq)

Question 19

What is the colour change when Iron(II) ion reacts to form a coloured hydroxide precipitate?

Answer 19

PALE GREEN solution → GREEN precipitate

Darkens on standing

Question 20

Express the ionic equation for the reaction between aqueous Iron(III) ion and NaOH (OH-).

Answer 20

[Fe(H2O)6]2+(aq) + 3OH-(aq) → Fe(OH)3(H2O)3 + 3H2O(l)

Question 21

Express the ionic equation for the reaction between aqueous Iron(III) ion and NH3.

Answer 21

[Fe(H2O)6]2+(aq) + 3NH3(aq) → Fe(OH)3(H2O)3 + 3NH4+ (aq)

Question 22

What is the colour change when Iron(III) reacts to form a coloured hydroxide precipitate?

Answer 22

YELLOW solution → ORANGE precipitate

Darkens on standing

Question 23

Express the ionic equation for the reaction between aqueous Manganese(II) ion and NaOH (OH-).

Answer 23

[Mn(H2O)6]2+(aq) + 2OH-(aq) → Mn(OH)2(H2O)4 + 2H2O (l)

Question 24

Express the ionic equation for the reaction between aqueous Manganese(II) ion and NH3.

Answer 24

[Mn(H2O)6]2+(aq) + 2NH3(aq) → Mn(OH)2(H2O)4 + 2H2O (l)