1c. Intermolecular Forces

Question 1

How do London Dispersion Forces arise?

Answer 1

1. Electron Wobble
2. Momentary separation of charge called Temp Dipole
3. Induced dipole
4. Electrostatic attraction between dipoles is LDF

Question 3

Why do boiling points of Noble Gases increase going down group

Answer 3

1. More electrons in atoms leads to greater cloud wobble
2. leads to greater separation of charge and larger dipoles
3. Electrostatic attraction between dipoles increases
4. requires more energy to break them
5. Boling points increase

Question 4

Why were the Noble Gases used to show existence of intermolecular attractions called LDF?

Answer 4

There is no other bonding going on in the Noble gases so differences in boiling points had to be down to attractions between atoms.

Question 5

Why do boiling points of halogens increase going down group?

Answer 5

1. More electrons in molecules leads to greater cloud wobble
2. leads to greater separation of charge and larger dipoles
3. Electrostatic attraction between dipoles increases
4. requires more energy to break them
5. Boling points increase

Question 6

What is a dipole?

Answer 6

A separation in charge within a molecule

Question 7

What is a polar covalent bond?

Answer 7

A n unequal sharing of electrons caused by atoms forming covalent bond having an en difference >0.5 and <2.0

Question 11

Why does sulphur have a higher melting point than phosphorous?

Answer 11

• Sulphur exists as S₈ molecules and phosphorous as P₄
• Greater number of electrons in molecule leads to greater dipoles
• Electrostatic attractions is therefore larger between di[poled molecules and requires more energy to break them
• Melting point is therfore higher

Question 12

How would you show a H-bond between 2 water molecules?

Answer 12

Question 13

What is the bonding continuum?

Answer 13

The type of bonding is determined by the difference in electronegativity between the elements involved.

Question 15

What is a non-polar (Pure) covalent bond?

Answer 15

An equal sharing of electrons between atoms with very similar en values

Question 16

What is a covalent bond? (Nat 5)

Answer 16

A shared pair of electrons

Question 17

Which 3 elements, if directly bonded to a H atom, will cause H-bonding to arise?

Answer 17

Nitrogen

Oxygen

Fluorine

Question 18

What is a hydrogen bond?

Answer 18

A strong dipole-dipole electrostatic attraction between molecules where h is bonded to a small, highly electronegative atom.

Question 21

How does electronegativity difference link to “covalent character” ?

Answer 21

The lower the electronegativity difference, the greater the covalent character

Question 22

How does electronegativity difference link to “Ionic character” ?

Answer 22

The greater the electronegativity difference, the greater the ionic character