Chapter 6

Question 1

What are the exceptions to the octet rule?

Answer 1

Beryllium (maximum of 4 electrons in valence shell)

Boron (maximum of 6 electrons in valence shell)

Hydrogen (maximum 2 electrons in valence shell)

Question 2

What is the difference between intramolecular force and and intermolecular forces

Answer 2

Intramolecular forces are strong forces between the bonded element Eg H2O - connection between the hydrogen and oxygen

Intermolecular forces are weak dispersion forces which hold together distinct molecules in a substances.
Eg H2O — H2O

Question 3

What are the properties of ionic compounds

Answer 3

• low melting and boiling points
• non conductors of electricity
• the solids are usually soft

Question 4

Why do covalent molecular substances have low melting and boiling points.

Answer 4

The intermolecular forces holding them together are weak.

This means less energy is needed to disturb the bond.

Question 5

Why are covalent molecular substances non -conductors of electricity

Answer 5

Because their electrons are immobile, as they either occupied or being shared. Therefore there is nothing to carry the electric current

Question 6

Why are covalent molecular substances usually soft

Answer 6

The molecules have weak dispersions forced holding them together making them feel soft.

Question 7

What are covalent molecular substances

Answer 7

They are substances formed through the sharing of electrons ( a covalent bond = a bond formed by the sharing of electrons between two non metallic atoms).
They have very strong intermolecular forces holding them together