Group 7-halogens

Question 1

what are group 7 elements known as?

Answer 1

the halogens

Question 2

what are the elements on group 7

Answer 2

• fluorine
• chlorine
• bromine
• iodine
• astatine

Question 3

why do group 7 elements exist as diatomic molecules?

Answer 3

because they share a pair of electrons in a covalent bond giving both toms a full outer shell

Question 4

what happens as you go down group seven ?

Answer 4

• melting and boiling points increase
• reactivity decreases
• Color becomes darker
• State of change gas to liquid to solid

Question 5

at room temperature what color is

1. chlorine
2. bromine
3. iodine

Answer 5

• chlorine: fairly reactive, poisonous green gas
• bromine: poisonous brown orange liquids gives off an orange vapor at room temp
• iodine: dark grey solid purple vapor when heated

Question 6

why does reactivity decrease going down group 7

Answer 6

• gain one electron to 1- ion
• as you go down the group, less reactive as it gets harder to gain extra electron to make full outer shell when its further away form the nucleuas

Question 7

what happens when halogens react with alkali metals

Answer 7

• form salts called metal halides
• eg : sodium+ chlorine → sodium chloride | 2Na+Cl₂ → 2NaCl
• eg: potassium + bromine → potassium bromide | 2K+Br₂→ 2KBr

Question 8

what is a displacement reaction?

Answer 8

• a displacement reaction is where a more reactive element displaces a less reactive element from a compound

Question 9

describe what happens in the chlorine water and potassium bromide practical

Answer 9

• chlorine is more reactive than bromine
• if you add chlorine water to potassium bromide
• chlorine will displace the bromine and becomes potassium chloride
• the bromide ions are oxidized to bromine turning orange

Question 10

write a balanced equation for chlorine and potassium bromide displacement reaction

Answer 10

chlorine + sodium bromide → sodium chloride + bromine

Cl₂(aq) + 2NaBr(aq) → 2NaCl(aq) + Br₂(aq)

Question 11

how can displacement reactions show reactivity trends

Answer 11

• start by adding small amount of halide solution in test tube
• add a few drops of a halogen solution to it and shake tube gently
• color change=reaction
• the halogen replaced the halide ions from salt
• no color change no reaction

Question 12

explain what is happening and what is made

Answer 12

when chlorine water is added to:

• potassium bromide solution-an orange solution is formed
• potassium iodide solution - a brown solution is formed

when bromine water is added to:

• potassium iodide solution- a brown solution is formed
• chlorine displaces both bromine and iodine . bromine only displaces iodine . Iodine doesn’t displace either

Question 13

Florine reaction with iron wool

Answer 13

• Reacts with almost anything instantly.
• dangerous

Question 14

Chlorine reaction with iron wool

Answer 14

Reacts with heated iron wool very quickly.

Question 15

Bromine reaction with iron wool

Answer 15

Has to be warmed and the iron wool heated. The reaction is faster.

Question 16

Iodine reaction with iron wool

Answer 16

Has to be heated strongly and so does the iron wool. The reaction is slow

Question 17

Why do boiling and melting points increase as you go doen group 7

Answer 17

• the molecules become larger
• the intermolecular forces become stronger
• more energy is needed to overcome these forces

Question 18

What is made when a halogen reacts with a non metal

use chlorine and hydrogen

Answer 18

• A compound is formed
• hydrogen + chlorine → hydrogen chloride
• H2(g) + Cl₂(g) → 2HCl(g)

Question 19

Describe the reaction between hydrogen and Florine

Answer 19

• Explodes at room temperature and in the dark, forming hydrogen fluoride

Question 20

Describe the reaction between hydrogen and chlorine

Answer 20

Explodes with a flame or in sunlight, forming hydrogen chloride

Question 21

Describe the reaction between hydrogen and bromine

Answer 21

• Vigorous reaction when warmed with hydrogen, forming hydrogen bromide

Question 22

Describe the reaction between hydrogen and iodine

Answer 22

• Very slow reaction when heated strongly, forming some hydrogen iodide

Question 23

What happens when the hydrogen halides are put into water

Answer 23

The hydrogen halides are gases at room temperature. They dissolve** in water to produce **acidic** **solutions.