Group 7, Halogens Flashcards
Fluorine, appearance and comments
Yellow gas.
The most reactive, toxic.
Chlorine, appearance and comments
Green gas.
Very reactive, toxic.
only used in small amounts so benefits outweigh risk
Bromine, appearance and comments
Used to identify saturated alkane.
Brown/orange liquid.
Very easily forms an orange vapour.
Often used as a solution in water (yellow-orange bromine water) this is less toxic.
Iodine, appearance and comments
Grey crystalline solid (regular stacked arrangement).
Very easily forms purple vapour.
Often used as a (sort of) solution in water (brown “iodine solution”).
Reactive and toxic.
Group 7 general comments
Simple covalent diatomic molecules. Forms Van der Vaal’s forces.
Trend in atomic radius
Increases down the group.
More shells down the groups, more shielding, bigger atoms.
Trend in electronegativity
Decreases down the group.
Bigger atoms/more shells, more shielding, weaker attractions between nucleus and 2 electrons in covalent bone.
Trend in melting and boiling point
Increases down the group.
Bigger molecules, more Van der Vaal’s forces, higher mpt/bpt between molecules.
Reaction of chlorine with water
Cl2(g) + H20(l) -
> HClO(aq) + HCl(aq)
disproportiononation reaction
other elements react similarly but much more slowly down the group
Alternative to the direct chlorination of swimming pools
Add solid sodium chlorate (1)
NaClO+ H2O (reversible arrow) Na^+ + OH^- + HClO
swimming pool would need to be kept slightly acidic as in alkaline solution equilibrium would move to the
left and HClO is needed to remove ClO^-
Reaction of chlorine with alkali to form bleach
Chlorine reacts with cold, dilute, sodium hydroxide to form sodium chlorate, the active ingredient in bleach and an oxidizing agent.
Cl2 + 2NaOH -> NaClO + NaCl + H2O
In sunlight, chlorine can also oxidize water slowly to form oxygen.give the equation for this
“Cl2 + “H2O-> 4HcL +O2
