Halogens (Group 7)

What colour and state is chlorine?

yellow - green gas

What colour and state is bromine?

red - brown liquid

What colour and state is iodine?

purple solid

What is the trend going down group 7 in terms of state?

• There is a trend in state from gas to liquid to solid down the group

• This is because the melting and boiling points increase as you go down the group

• From this, you can predict that any halogens above chlorine will be gases (their boiling points will be even lower), and any below iodine will be solids (their melting points will be even greater)

What is displacement?

Displacement is the process where an atom in a compound is replaced by a more reactive compound.

Halogens come in groups of_____. What is this called?

• Halogens come in pairs

• This is called diatomic molecules

• It is where two of the same group 7 element form a covalent bond and share an electron to have a full outer shell.

What is the trend going down group 7 in terms of reactivity?

• As you go down group 7, the reactivity decreases

• This is because the less energy shells the halogen has, the more reactive it is because the outer energy level is closer to the nucleus and so the force of attraction between the nucleus and another element’s outer shell is greater.

Halide

Where a halogen gains an electron and becomes a 1- charged ion

What is the chemical equation for displacement in group 7?

E.g potassium bromide + chlorine —> potassium chloride + bromine

2KBr + Cl₂ —> 2KCl +Br₂