Module 5 - [ch24] Transition elements

Question 1

What are transition elements?

Answer 1

D-block elements that form at least 1 ion with a partially filled d-orbital

Question 2

Which elements are in the D-block but not transition metals. Why?

Answer 2

Zinc and Scandium
Zn / Sc

Zinc has a full filled D-orbital
Scandium’s ion (Sc3+) has an empty D-orbital

Question 3

What are 3 properties of transition metals

Answer 3

Form coloured compounds
They form compounds in which the transition elements has different oxidation states - variable oxidation states
The elements and their compounds can act as catalysts

Question 4

What is a catalyst

Answer 4

A substance that can be used to increase the rate of reaction without being used up

Question 5

How do catalysts increase the rate of reaction

Answer 5

They provide an alternative reaction pathway with a lower activation energy

Question 6

Give two examples when transition metals are used as catalysts

Answer 6

Haber process - nickel catalyst
Contact process - Vanadium Oxide

Question 7

What is the difference between homogenous and heterogenous catalysts?

Answer 7

Homogenous - when the catalyst is in the same physical state as the reactants

Question 8

Define Ligand

Answer 8

Molecule or ion that donates a lone pair of electrons to a central metal ion to form a co-ordinate bond

Question 9

what is a co-ordinate bond

Answer 9

a dative bond
where both electrons involved in the bond are donated from one of the bonded atoms

Question 10

What is a co-ordination number

Answer 10

The number of co-ordinate bonds attached to the central metal ion

Question 11

How are complex ion formed

Answer 11

When one or more molecules or negatively charged ions bond to a central metal ion

Question 12

What is the difference between monodentate and bidentate ligands

Answer 12

monodentate - a ligand that donates one pair of lone electrons to the central metal ion

bidentate - a ligand that donates two lone pairs of electrons to the central metal ion

Question 13

What are the 5 most common monodentate ligands and their charges?

Answer 13

h2o - neutral
Nh3 - neutral
Cl -1
OH -1
CN -1

Question 14

What are the 2 most common bidentate ligands?

Answer 14

1,2diaminoethane
ethanedioate

Question 15

What do ligands 1,2diaminoethane and ethanedioate share in common?

Answer 15

the both form two coordinate bonds

Question 16

What is the shape and bond angle of six-coordinate complexes?

Answer 16

octahedral
90 degrees

Question 17

What is the shape and bond angle of four-coordinate complexes?

Answer 17

tetrahedral
109.5

Question 18

define stereoisomers

Answer 18

the same structural formula but different arrangements in space

Question 19

How is stereoisomerism different in complex ions in comparison to organic chemistry?

Answer 19

In organic chemistry Cis/Trans isomerism requires the presence of a C=C which restricts rotation
No double bond is involved with complex ions, cis and trans isomers are defined by the orientation of ligands

Question 20

What are optical isomers?

Answer 20

Non-superimposable mirror images of each other

Question 21

What are optical isomers also known as?

Answer 21

enantiomers

Question 22

When does optical isomerism occur

Answer 22

In octahedral complexes where there are at least 2 bidentate ligands

Question 23

what is ligand substitution

Answer 23

When one ligand in a complex ion is replaced by another ligand

Question 24

Ligand substitution with ammonia

Answer 24

[Cu(H2O)6]2+(aq) + 4NH3(aq) - > [Cu(NH3)4(H2O)2]2+(Aq) + 4H2O(l)

hexa aqua copper(II) ions + ammonia

[Cu(H2O)6]2+(aq) - pale blue
dropwise - Cu(OH)2 - light blue precipitate
excess - tetra di amine di aqua copper (II) - dark blue - precipitate dissolved

Question 25

Ligand substitution with chloride ions

Answer 25

[Cu(H2O)6]2+(aq) + 4Cl-(Aq) -> [CuCl4]2- + 6H2O(l)

HCl can be used as a source of chloride ions
pale blue -> yellow

Question 26

In ligand substitution with chloride ions, how come the co-ordination number changes

Answer 26

Cl- ligand is larger in size than the H2O ligand
Therefore takes up more space so fewer Cl ligands fit around the central metal ion