Group 7: Groups in the periodic table: Chemistry: GCSE (9:1)

Name of Group 7 elements

The halogens

Group 7 elements have similar chemical properties

because they all have 7 outer shell electrons

Diatomic molecule

A molecule consisting of two atoms

Chemical structure of group 7

Diatomic molecules

Pattern in melting points and boiling points down group 7

Melting and boiling points decrease

Pattern of reactivity down the halogens

They get less reactive

Reason for patterns in reactivity

Larger atomic radius, more shielding, less nuclear attraction, harder to gain a reaction

Group 7 elements react by

gaining 1 electron

Displacement reaction

A reaction in which a more reactive element replaces a similar element in a compound

Potassium bromide + Chlorine -->

Potassium chloride + Bromine

Sodium chloride + Bromine -->

No reaction

Sodium iodide + Bromine -->

Sodium bromide + Iodine

Chlorine

A yellow-green gas which when dissolved in water is used as a disinfectant

Bromine

A corrosive red-brown liquid

Iodine

A shiny grey solid, which sublimes easily forming a purple vapour

Test for chlorine

Bleaches damp litmus paper

Reduced in displacement

More reactive halogen

Oxidised in displacement

Less reactive halogen