3.1.3 The halogens Flashcards
What group elements are referred to as halogens?
group 7
Properties of halogens
- Low melting and boiling points
- Exist as diatomic molecules
What is the trend in boiling point down group 7?
Why?
Increases down the group because:
- size of atom increases as more occupied electron shells thus stronger london forces of attraction between molecules takes more energy to break
What is the trend in reactivity down group 7?
Why?
Reactivity decreases because:
- Atomic radius increases
- Electron shielding increases
- Ability to gain an electron and form 1- ions decreases
What is the trend in oxidising ability down the group? Why?
Decreases down group (Cl strongest, I weakest). This is because Cl has the fewest occupied electron shells, greatest force of attraction between outer electrons and nucleus and thus is the easiest to gain and be reduced therefore the best oxidising agent
What is the trend in reducing ability of the halides down the group?
Why?
Increases down the group. This is because I has the most occupied electron shell so outer electrons are further from the nucleus, weakest force of attraction between outer electrons and positive charge of nucleus and thus is the easiest to be oxidised and lose electrons therefore the best reducing agent.
WHen a more reactive halogen displaces a less reactive halide what is the reaction called?
Displacement reaction
What is the colour of chlorine in water?
Pale green
What is the colour of bromine in water?
Orange
What is the colour of Iodine in water?
Brown
What is the colour of chlorine in cyclohexane?
Pale green
What is the colour of bromine in cyclohexane?
Orange
What is the colour of iodine in cyclohexane?
Violet
Out of the 3 halides Cl-. Br- and I- which one of these can be oxidised by chlorine
Br- and I- ions
Write the equation for chlorine oxidising bromide ions
Cl₂ (aq) + 2Br- (aq) -> 2Cl- (aq) + Br₂ (aq)
