Unit 1-Transition Metals

Question 1

Why are transition metals known as d block elements?

Answer 1

The d block transition metals are metals with an incomplete d subshell in at least one of their ions.

Question 2

Explain why Copper and Chromium appear not to follow the aufbau principle (orbitals are filled in order of increasing energy).

Answer 2

Chromium would be expected to have [Ar] 3d4 4s2 but is actually [Ar] 3d5 4s1

Copper would be expected to have [Ar] 3d9 4s2 but is actually [Ar] 3d10 4s1

Cr and Cu acquire half-filled and fully-filled configurations which gives them extra stability.

Question 3

What is the electron configuration of Co²⁺ ?

Answer 3

[Ar] 3d7

Question 4

Explain why Scandium and Zinc are often considered not to be transition metals.

Answer 4

Scandium only forms 3+ ions and Zinc only forms 2+ ions. Neither of these result in an incomplete d subshell, therefore do not fit the definition of a transition metal.

Question 5

Consider the electronic configurations of the Fe²⁺ and Fe³⁺ ions in terms of orbital box notation. Explain why Fe(III) compounds are more stable than Fe(II) compounds.

Answer 5

Fe³⁺ ions would have a half-filled d subshell which is stable.

Question 6

What are the oxidation states of sulphur in H₂S, S₈ (elementary sulphur), SO₂, SO₃, and H₂SO₄ ?

Answer 6

H₂S, S₈ (elementary sulphur), SO₂, SO₃, and H₂SO₄

-2, 0, +4, +6 and +6.

Question 7

Define oxidation and reduction in terms of oxidation number

Answer 7

OXIDATION can be defined as an increase in oxidation number, while REDUCTION can be defined as a decrease in oxidation number.

Question 8

What is a transition metal complexes?

Answer 8

A complex consists of a central metal ion surrounded by ligands

Question 9

What is a ligand?

Answer 9

Ligands are electron donors which may be negative ions or molecules with non-bonding pairs of electrons.

Question 10

What is meant by a dative/coordinate bond?

Answer 10

a covalent bond (a shared pair of electrons) in which both electrons come from the same atom.

Question 11

How many pairs of electrons do each of the following types of ligands donate?

i) monodentate
ii) bidentate
iii) polydentate

Answer 11

i) one
ii) two
iii) more than one

Question 12

One nickel(II) ion will form six bonds with one ‘molecule’ of EDTA

i) What type of ligand is EDTA?
ii) what is the coordination number of nickel?

Answer 12

i) polydentate or hexadentate
ii) 6

Question 13

i) Name this complex.

[Fe(OH₂)₆]²⁺

ii) What is the coordination number of the transition metal ion?
iii) What is the oxidation state of the metal ion?

Answer 13

i) Hexaaquaferrate(II)
ii) 6
iii) +2

Question 14

i) Name this complex

[CrF₄]^-

ii) What is the coordination number of the transition metal ion?
iii) What is the oxidation state of the metal ion?

Answer 14

i) tetrafluorochromate(III)
ii) 4
iii) +3

Question 15

i) Name this complex

[Cu(CN)₆]^4-

ii) What its coordination number of the transition metal ion?
iii) What is the oxidation state of the metal ion?

Answer 15

i) hexacyanocuprate(II)
ii) 6
iii) +2