Van Der Waals' Forces

Question 1

what is a dipole

Answer 1

A molecule with 2 different charges

Question 2

What is an induced dipole-dipole force

Answer 2

Elecrons move randomly and therefore distort polarity.
Induces a temporary dipole, causing an attraction between a molecule

Question 3

Permanent dipole-dipole attraction

Answer 3

works for molecules which have an overall dipole.
There are attractions between permanent dipoles in neighbouring molecules

Question 4

hydrogen bonding

Answer 4

permanent dipole-dipole but occurs when a H is bonded to:
- fluorine
- oxygen
- nitrogen

Question 5

Strength of intermolecular forces:

Answer 5

h-bonding > permanent dipole-dipole > van der Waals’

this means that H-bonding has a higher boiling point.

Question 6

what is a lone pair of electrons

Answer 6

a pair of electrons in a valence shell that are no involved in bonding

Question 7

What happens to boiling points down a group

Answer 7

they increase

Question 8

why do boiling point increase down a group

Answer 8

• number of electron increase
• strength of intermolecular forces increase (more electrons = greater strength)

Question 9

why are boiling points of Group 4 hydrides lower than hydrides of Groups 5, 6 and 7

Answer 9

5, 6 and 7 are more likely to have dipole-dipole