Covalent Bondng & Structure

Question 1

Describe the structure and bonding of a macro molecule.

Answer 1

C - giant covalent lattice
B - many strong covalent bonds
D - strong electrostatic force of attraction between a bonding pair of electrons and the nuclei of the bonded atoms

Question 2

Describe the bonding and structure of simple molecules.

Answer 2

C - simple molecular
B - strong covalent bonds between atoms but, weak intermolecular forces between molecules
D - “depends on IMF”

Question 3

Why is a covalent bond described as localised?

Answer 3

The attraction is localised acting solely between the shared pair of electrons and the nuclei of the bonded atoms

Question 4

Why can some elements have an expanded octet?

Answer 4

Due to the availability of the 3d sub shell (up to 18 electrons in the outer shell)

Question 5

What is a dative covalent or coordinate bond?

Answer 5

• The shared pair of electrons has been supplied by one of the bonding atoms only.
• The shared electron pair was originally a lone pair of electrons of one of the bonded atoms.

Question 6

Why do simple molecular substances have low melting and boiling points?

Answer 6

• weak intermolecular forces that only require little energy to be broken
  —> covalent bonds do not break!! as they are strong

Question 7

Describe and explain the solubility of non-polar simple molecular substances.

Answer 7

Non-polar solvents:
-intermolecular forces form between the molecules and the solvent
- interactions weaken the intermolecular forces in the simple molecular lattice
- so IMF’s break and the compound dissolves

Polar solvents:
- little interactions between molecules in the lattice and the solvent molecules
- intermolecular bonding within the polar solvent is too strong to be broken
- so non-polar simple molecules tend to be insoluble in polar solvents

Question 8

Describe and explain the solubility of polar simple molecular substances.

Answer 8

1. May dissolve in polar solvents
   —> polar solute molecules and polar solvent molecules can attract each other
2. Depends on the strength of the dipole

Question 9

Describe and explain the electrical conductivity of simple molecular substances.

Answer 9

Non-conductors of electricity
—> no mobile charge particles

Question 10

Describe and explain the melting and boiling points of giant covalent structures.

Answer 10

High melting and boiling points
—> strong covalent bonds which require lots of energy to break

Question 11

Are macro-molecules soluble?

Answer 11

No

Question 12

Describe and explain the conductivity of macro-molecules.

Answer 12

1. Giant covalent lattices are nonconductors
   —> no mobile charge carriers
2. Graphene and graphite can conduct
   —> delocalised electrons are free to move and carry a charge