Group 7 - Halogens

Question 1

What are the ‘halogens’?

Answer 1

Question 2

What are the colours and physical states of chlorine, bromine and iodine at room temperature?

Answer 2

Chlorine

• Green gas

Bromine

• Red-brown liquid

Iodine

• Dark grey crystalline solid

Question 3

Describe the things that change about the halogens as you go down group 7.

Answer 3

• They become less reactive
• Their melting and boiling points increase
• The colours of the halogens get darker

Question 4

(Exam-style question)

Answer 4

• Colour: grey / black
• State: solid

Question 5

Explain the trend in reactivity for the halogens.

Answer 5

• The halogens each have seven electrons in their outer shell
• As you go down the group, the halogens become less reactive
• This is because the atomic radius increases and it becomes harder to attract the extra electron to fill the outer shell

Question 6

Describe the test to show that a gas is chlorine.

Answer 6

• Place damp, blue litmus paper into the chlorine gas
• It might first turn red because a solution of chlorine is acidic
• It would then turn white

Question 7

What reaction forms salts called ‘metal halides’?

Answer 7

Halogens reacting with metals

Question 8

(Exam-style question)

Answer 8

Question 9

(Exam-style question)

Sodium reacts violently with fluorine, at room temperature, to form sodium fluoride.

Predict how astatine might react with sodium at room temperature. Explain your answer.

Answer 9

• Both astatine and fluorine have 7 outer shell electrons, so they react similarly
• Astatine will react with sodium to form sodium astatide
• However, astatine will react more slowly than fluorine as reactivity decreases down the group

Question 10

What reaction forms hydrogen halides?

Answer 10

Halogens reacting with hydrogen

Question 11

Explain how hydrogen halides can form acidic solutions.

Answer 11

They can dissolve in water to form acidic solutions because they are soluble

Question 12

(Exam-style question)

Answer 12

Hydrobromic acid