Section 3 - Intermolecular Bonding

Question 1

1. What is an intermolecular bond?
2. How does it contrast the bonds between atoms?

Answer 1

1. Weak force of attraction between the molecules
2. Bonds between atoms are very strong

Question 2

How does strength of intermolecular bond affect boiling point?

Answer 2

When melting/boiling the intermolecular bonds are broken
If stronger, more energy needed to break, leads to higher boiling point

Question 3

What 2 things can affect intermolecular bond strength?

Answer 3

1. Number of electrons in molecule - More electrons means stronger intermolecular bonds
2. Surface area of molecule - Larger surface area over which intermolecular bonds can act, stronger intermolecular bond

Question 4

What is electronegativity?

Answer 4

Ability of an atom to attract electrons in covalent bond

Question 5

How does electronegativity change down a group and across a period?

Answer 5

Decreases down a group
Increases across a period

Question 6

What is a polar bond?

Answer 6

A bond between 2 atoms with different electronegativity. Bonding electrons will be more strongly attracted to the atom with higher electronegativity

Question 7

How do polar bonds affect strength of strong intermolecular forces?

Answer 7

Polarises the molecule, makes one end slightly positive and other slightly negative.
Oppositely charged end of different molecules attract making it harder to separate them.

Question 8

Why do fluorine, oxygen and nitrogen bonded to hydrogen create strong intermolecular forces.

Answer 8

Hydrogen atom is strongly polarised by the very electronegative F,O and N atoms.

Question 9

How is a hydrogen bond formed?

Answer 9

Slightly positive hydrogen atoms attract to lone pair of electrons in a nearby molecule

Question 10

What is the strongest type of intermolecular attraction?

Answer 10

Hydrogen bonds