Group 7, the Halogens: Trends in Properties

Question 1

How do the boiling points of the halogens changes as you descend the group?

Answer 1

• Boiling points increase

Question 2

Why does the boiling point of halogens increase as you descend the group?

Answer 2

• As you descend group, the relative mass of the molecules increase
• More electrons mean stronger van der Waals forces between the molecules
• Requires more energy to break these intermolecular forces

Question 3

How does the electronegativity of halogens change as you descend the group?

Answer 3

• Electronegativity decreases

Question 4

Why does the electronegativity of halogens decrease as you descend the group?

Answer 4

• The atomic radius and shielding increases
• Therefore a weaker attraction between the nucleus and bonding pair of electrons in a covalent bond

Question 5

What kind of agents are the halogens?

Answer 5

• Oxidising agents
• Gain an electron when reacting

Question 6

How does the oxidising ability of halogens change as you descend the group?

Answer 6

• Oxidising ability decreases

Question 7

Why does the oxidising ability of halogens decrease as you descend the group?

Answer 7

• The atomic radius and shielding increases
• Therefore reducing the ability of the halogen to attract electrons

Question 8

Can halogens displace other halide ions?

Answer 8

• A halogen will displace a halide from solution if the halide is below it in the periodic table
• E.g chlorine can displace bromide ions, but chloride ions are displaced by fluorine

Question 9

Chlorine water, bromine water and iodine solution are reacted with potassium chloride, potassium bromide and potassium iodide. Which will react?

Answer 9

• Chlorine water and potassium bromide
• Chlorine water and potassium iodide
• Bromine water and potassium iodide

Question 10

What colour is the solution formed when chlorine water and potassium bromide react? What substance is produced?

Answer 10

• Orange solution
• Br₂ formed

Question 11

What colour is the solution formed when chlorine water reacts with potassium iodide? What substance is produced?

Answer 11

• Brown solution
• I₂ formed

Question 12

What colour is the solution formed when bromine water reacts with potassium iodide? What substance is produced?

Answer 12

• Brown solution
• I₂ formed