LECTURE 5 (Coordinating compounds)

Question 1

Describe Ionic compounds

Answer 1

• Consist of positive and negative ions
• Ions held together by ionic bonds (strong attractions between oppositely charged ions)

Question 2

What is a Covalent bond?

Answer 2

When atoms of two non-metals share electrons

Question 3

What does the high ionisation energies of the non-metals cause?

Answer 3

Electrons are not transferred between atoms but shared to achieve stability

Question 4

What is the difference between a covalent bond and molecules?

Answer 4

Covalent bond = when atoms share electrons

Molecules = when two or more atoms share electrons

Question 5

What is a dipole?

Answer 5

A polar covalent bond that has a separation of charges

Question 6

Describe how the polarity of a bond depends on the electronegativity difference

Answer 6

In a polar covalent bond, the shared electrons are attracted to the more electronegative electron -> makes it partially -ve -> other atom with lower electronegativity becomes partially +ve due to lack of electrons at that atom -> bond becomes MORE POLAR as the ELECTRONEGATIVITY DIFFERENCE increases

Question 7

Who was the first to formulate the ideas of the structures of coordination compounds?

Answer 7

Alfred Werner (1866-1919)

Question 8

What are coordination compounds?

Answer 8

Chemical compounds that consist of an array of anions or neutral molecules that are bound to a central atom via coordinate covalent bonds

Question 9

What are the molecules/ions that are bound to the central atom in coordination compounds referred to as?

Answer 9

Ligands/Complexing agents

Question 10

How strong is the bond between metal and ligand?

Answer 10

Stronger than intermolecular forces (because they form directional bonds between the metal ion and the ligand) but are weaker than covalent bonds and ionic bonds

Question 11

What is the difference between a double salt and a complex?

Answer 11

Double salt = dissociate into simple ions completely when dissolved in water

Complex ions = do not dissociate

Question 12

What do double salts and a complex have in common?

Answer 12

Both are formed by the combination of two or more stable compounds in stoichiometric ratio

Question 13

What are Isomers?

Answer 13

Two or more compounds that have the same chemical formula but a different arrangement of atoms

Question 14

What are the two principal types of isomerism known among coordination compounds?

Answer 14

• Stereoisomerism
• Structural isomerism

Question 15

What are the two types of Stereoisomerism?

Answer 15

• Geometrical isomerism
• Optical isomerism

Question 16

What are the different types of Structural isomerism?

Answer 16

• Linkage isomerism
• Coordination isomerism
• Ionisation isomerism
• Solvate isomerism

Question 17

What are Stereoisomers?

Answer 17

Have the same chemical formula and chemical bonds but have different spatial arrangement

Question 18

What are Optical isomers/Enantiomers?

Answer 18

Mirror images that cannot be superimposed on one another

Question 19

What is the Valence bond theory?

Answer 19

The metal atom or ion under the influence of ligands can use its orbitals for hybridisation to yield a set of equivalent orbitals of definite geometry (e.g octahedral tetrahedral)

Question 20

What is the Crystal field theory?

Answer 20

An electrostatic model which considers the metal-ligand bond to be ionic arising purely from electrostatic interactions between the metal ion and the ligand

Question 21

What are the advantages and disadvantages of the Crystal field model?

Answer 21

ADVANTAGES:
- explains the formation, structures, colour and magnetic properties of coordination compounds

DISADVANTAGES:
- does not take into account the covalent character of bonding between the ligand and central atom