2.3.1 Physical Properties of Group 7

Question 1

How can chlorine, bromine and iodine be used in life?

Answer 1

Chlorine - bleaching agent
Bromine - Flame retardants and fire extinguishers
Iodine - Antiseptic and disinfectant

Question 2

What are the colours of the halogens?

Answer 2

F2 - Yellow gas
Cl2 - Green gas
Br2 - Orange/brown liquid
I2 - Grey/black solid, or purple vapour

Question 3

What is volatility?

Answer 3

How easily a substance evaporates

Question 4

How does volatility change going down group 7?

Answer 4

Going down the group, the boiling point of elements increases so the volatility of elements decreases.

Fluorine most volatile, iodine least volatile

Question 5

How does a covalent bond work?

Answer 5

• Orbitals overlap so electrons are shared between atoms
• Bonding pair of electrons is attracted to the nuclei of the atoms

Question 6

What is the trend in bond enthalpy going down group 7?

Answer 6

• Bond enthalpy decreases
• Atomic radii increases, less attraction between outer electrons and nuclei
• Exception is fluorine, because it is so small their lone pairs are so close to each other that they have significant repulsion counteracting attraction between bonding pair of electrons and nuclei.

Question 7

How do van der waals forces occur in halogens?

Answer 7

• Instantaneous dipoles occur when more electrons happen to be at one end of the molecule
• This can induce instantaneous dipoles in other diatomic molecules around it

Question 8

Why does melting point / boiling point increase going down group 7?

Answer 8

• As you go down, the size of the atom increases
• So more electrons present
• So more induced instantaneous dipoles occur
• More van der waals forces
• So more energy required to overcome these forces of attraction
• Hence volatility decreases