2(b) Group 7 (Halogens)

what are the group 7 halogens?

fluorine, chlorine, bromine, iodine, astatine

properties of the halogens (2) (F, Cl, Br, I at room temperature, characteristics, colour in solution)

poisonous non-metals

diatomic

fluorine: yellow gas, very reactive + poisonous

chlorine: pale yellow-green gas, reactive, poisonous + dense, pale green in solution

bromine: red-brown liquid, dense red-brown volatile liquid, orange in solution

iodine: grey solid, shimmery crystalline solid that sublimes to form a purple vapour, dark brown in solution

what type of ions do the halogens form?

1- ions

how does reactivity change in the group?

how do melting/boiling points change?

how does their physical state change?

the halogens get less reactive as you move down the group, and their rates of reaction get slower

melting/boiling points increase as you go down the group due to the atoms getting larger and IM forces increasing, requiring more energy to overcome

At room temperature, their physical states get closer to solid (F + Cl are gases, Br is a liquid, I is a solid)

explain the reactivity trend in the group

halogens get less reactive as you move down the group

in order to form ions of -1 charge, halogens have to gain an electron

as you move down the group, electron shells are added

the outer shell is therefore further away from the nucleus, making it harder for the atom to gain an electron

the halogens therefore get less reactive as more electron shells are added

when does a halogen displacement reaction occur?

when a more reactive halogen displaces a less reactive halogen from an aqeous solution of its halide (an ionic halogen compound)

what is the order of reactivity of the first 3 halides, and what can they displace?

Cl, Br, I

Chlorine can displace both bromine and iodine

Bromine can displace only iodine

Iodine cannot displace either

what is the equation for when chlorine reacts with potassium bromide or potassium iodide?

what observations can be made when these reactions occur?

Cl₂ + 2KBr → 2KCl + Br₂

Cl₂ + 2KI → 2KCl + I₂

solution turns orange as bromine is formed

solution turns brown as iodine is formed

what is the equation for when bromine reacts with potassium iodide?

what observation can be made when this reaction occurs?

Br₂ + 2KI → 2KBr + I₂

solution turns brown as iodine is formed