3.1.3 - The halogens

a) List the two main properties of halogens?

• Exists as diatomic molecules

• Low melting/ boiling points

b) What ions does halogen have?

-1 ion

c-d) What is the trend of reactivity down the group?

• Reactivity decreases

• Due to AR increases

• Electron shielding increases due to more electron shells and electrons

• Less energy required to remove an electron

• Ability to gain an electron and form 1- ions decreases

What is the trend of boiling points down the group?

Increases down the group:

• Size of an atom increases

• More occupied electron shells 

• Stronger London forces to overcome attraction between molecules - require more energy 

e) What is the trend of oxidising ability down the group?

• Decreases down the group

• Example Chlorine is the strongest since it has the greater force of attraction between outer electrons and nucleus

• Easiest to gain electrons and reduced

• Oxidising agent

What is the trend of reducing ability of halides down the group?

• Increases down the group

• Iodine is the strongest because it has the most occupied electron shell, further way from the nucleus

• Weakest force of attraction between outer electrons and positive charge of nucleus

• Easiest to lose electrons and be oxidised - reducing agent  

Explain disproportionation?

The oxidation and reduction of the same element in a redox reaction

ei) What is the equation of chlorine and water?

Cl₂ (g)+ H₂ O(l) ——→ HClO (aq) + HCl (aq)

What type of reaction is the reaction of chlorine with water?

Disproportionation and chlorine is oxidised and reduced 

Why is chlorine added to drinking water and what are the consequences?

To purify water

However is toxic/ poisonous

eii) What is the equation of forming bleach?

Cl₂ (aq) + 2NaOH (aq) ——> NaCl( aq) + NaClO (aq) +H₂O (l)

NaClO = bleach

When a more reactive halogen displaces a less reactive halide what’s the reaction called?

Displacement Reaction