The Halogens Flashcards
What group are referred to as the halogens?
Group 7
List 2 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 group because:
Size of atom increases as more occupied electron shells —> stronger London forces of attraction between molecules, take 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 am 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 electrons and be reduced —> best oxidising agent.
What is the trend in reducing ability of the halide down the group? Why?
Increases down the group (Cl- weakest, I- strongest)
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 us the easiest to be oxidised and lose electrons —> best reducing agent
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
Define disproportionation
The oxidation and reduction of the same element in a redox reaction.
What is the equation for the reaction of Cl2 with water?
Cl2 (g) + H2O (l) —> HClO (aq) + HCl (aq)
What type of reaction is the reaction of chlorine with water?
Disproportionation; chlorine is both oxidised and reduced
