8.2 Group 7

Question 1

What is the alternative name for group 7/17 elements?

Answer 1

Halogens

Question 2

How reactive are halogens?

Answer 2

They are the most reactive non-metallic group

Question 3

What kind of molecule do all halogens exist as at RTP?

Answer 3

Diatomic molecules. (X2)

Question 4

Describe the arrangement of the electrons in the outer shell of halogens.

Answer 4

7 electrons in the outer shell, 2 subshells, S2P5

Question 5

Are halogens oxidising or reducing agents?

Answer 5

Oxidising

Question 6

Does the reactivity of halogens increase or decrease going down the group

Answer 6

Decrease

Question 7

How can you tell the difference between a bromine solution and an iodine solution?

Answer 7

Mix them both with cyclohexane. Bromine will appear orange, Iodine will appear violet.

Question 8

Does boiling point increase or decrease going down group 7? Why?

Answer 8

-Increases.
-More electrons, stronger London forces, more energy required to break intermolecular forces, boiling point increases.

Question 9

Explain why reactivity changes going down group 7.

Answer 9

-Atomic radius increases
-Electron shielding increases
-Less nuclear attraction to capture an electron from another species
-Reactivity decreases

Question 10

What is disproportionation?

Answer 10

A redox reaction in which the same element is both oxidised and reduced.

Question 11

Give 2 examples of disproportionation reactions involving group 7/17 elements.

Answer 11

Cl2 + H2O, and Cl2 + 2NaOH

Question 12

What is the primary use of chlorine?

Answer 12

Used to kill bacteria. Treats drinking water and swimming pool water.

Question 13

What is one of the major problems with using chlorine in water?

Answer 13

Leaked chlorine can react with organic hydrocarbons, forming chlorinated hydrocarbons, suspected of causing cancer

Question 14

How do you test for halide ions?

Answer 14

Aqueous halide ions can react with aqueous silver ions to form precipitates of silver halides.