Sc17b - Group 7 Halogens

Question 1

Properties of halogens

Answer 1

• form covalent diatomic molecules
• non metallic - poor conductors of heat and electricity
• toxic - corrosive.
  -become less reactive as down the group

Question 2

How do halogens change going down group 7?

Answer 2

Mp bp and density all increase down the group.

Question 3

What are the colours and States of chlorine bromine and iodine

Answer 3

Cl2 - pale / green gas
Br2 - red / brown liquid
I2 - purple / black solid (dark grey)

Question 4

How do we test for chlorine gas

Answer 4

Insert damp litmus paper into a test tube containing a gas. Damp blue litmus paper turns red and then bleaches if chlorine present.

Question 5

How do halogens react with metals and hydrogen ?

Answer 5

Halogen + metal -> metal halide (salt)
Halogen + hydrogen -> hydrogen halides
Hydrogen halide + water -> hydrohalic acid. E.g hcl

Question 6

Common use of halides

Answer 6

Sodium chloride - table salt
Sodium flouride - toothpastes
Sodium bromide - disinfectant
Sodium iodide - added to table salt to prevent iodide deficiency.

Question 7

Common use of all halides

Answer 7

Disinfectant and bleaches as they kill microorganisms and remove the colour from materials.

Question 8

Why do halogens become less reactive as you go down the group ?

Answer 8

More electron shells means More distance between outer electron, so because of the weaker attraction between the positive nucleus and the negative electron, it is harder for electrons to be gained.

Question 9

What are halogen ions called ?

Answer 9

Halides