Topic 15 Transition Metals

Question 1

What is a transition metal?

Answer 1

An element which forms one or more stable ions which have incompletely filled d orbitals.

Question 2

What are the physical properties of transition metals?

Answer 2

They are hard, have high melting points and have high boiling points.

Question 3

What role does the energetics of a process have on the ionic compound formed?

Answer 3

The compound formed is the compound which has the most energy released.

Question 4

How can the ionic compound formed be identified?

Answer 4

The energy released needs to be calculated by the sum of the ionisation energies and either the lattice enthalpy (if solid) or hydration enthalpy (if aqueous).

Question 5

Why do transition metal ions form lots of different colours when aqueous?

Answer 5

This is because of the different wavelengths of light absorbed.

When one wavelength of the visible spectrum is absorbed, all other wavelengths are reflected or travel through, therefore there is only one colour present to our eyes.

Question 6

What is a complex ion?

Answer 6

An ion in which a number of molecules or anions are bound to a central metal cation by co-ordinate bonds.

Question 7

What is a ligand?

Answer 7

A molecule or anion bound to the central metal ion in a complex ion by co-ordinate bonding.

Question 8

What is the co-ordinate number of an ion?

Answer 8

In a complex, this is the number of co-ordinate bonds there are from the surrounding ligands on the central metal ion.

Question 9

What is a co-ordinate bond?

Answer 9

A co-ordinate bond or dative covalent bond, is a bond of which both bonding electrons come from the same atom.

Question 10

What are monodentate, bidentate and multidentate ligands?

Answer 10

Monodentate - A ligand that forms one co-ordinate bond with the central metal ion in a complex

Bidentate - A ligand that forms two co-ordinate bond with the central metal ion in a complex

Multidentate - A ligand that forms more than two co-ordinate bond with the central metal ion in a complex.

Question 11

What are chelates?

Answer 11

Complex ions that contain multidentate ligands.

Question 12

What is an amphoteric hydroxide?

Answer 12

A hydroxide that can dissolve in either aqueous acid or aqueous alkaline.

Question 13

What are heterogenous and homogenous catalysts?

Answer 13

Heterogenous - A catalyst that is in a different state from the reactants. (They can generally be separated out from the reaction products easily).

Homogenous - A catalyst that is in the same state as the reactants.

Question 14

What is adsorption?

Answer 14

A process in which atoms, molecules or ions are held onto the surface of a solid.

Question 15

What is desorption?

Answer 15

This is the opposite of adsorption when atoms, molecules or ions are released from a solid surface.

Question 16

How do you name complex ions?

Answer 16

1. Name the number of ligands –> di, tri, tetra etc.
2. Name the type of ligands –> aqua (water), hydroxo (hydroxide), ammine (ammonia), chloro (chloride) etc.
3. Name the metal –> Iron, copper etc.
4. Name the oxidation number of the metal –> (ii), (iii) etc.

Question 17

What are the colours of the different oxidation states of vanadium?

Answer 17

2+ = Purple
3+ = Dark Green (may appear black)
4+ = Blue
5+ = Yellow

Question 18

How do you convert dichromate ions (Cr₂O₇²⁻) into chromate ions (CrO₄²⁻)?

Answer 18

2CrO₄²⁻ + 2H⁺ ⇌ Cr₂O₇²⁻ + H₂O

More Acid (H⁺) --> More dichromate ions
More Alkali (H₂O) --> More chromate ions

Question 19

What is ligand exchange?

Answer 19

The substitution of ligands in a complex ion.

During exchange, ions could be different sizes causing a ligand to substitute one or more previously existing ligands.

Question 20

What are the three ligand exchange reactions that you need to know?

Answer 20

H₂O/OH⁻ –> [Cu(H₂O)₆]²⁺ + 2OH⁻ ⇌ [Cu(H₂O)₄(OH)₂] + 2H₂O

OH⁻/NH₃ –> [Cu(H₂O)₄(OH)₂] + 4NH₃ ⇌ [Cu(NH₃)₄(H₂O)₂] + 2H₂O + 2OH⁻

H₂O/Cl⁻ –> [Cu(H₂O)₆]²⁺ + 4Cl⁻ ⇌ [CuCl₄]²⁻ + 6H₂O