Group 7 (Halogens)

Question 1

What are the elements in group 7? (In order of reactivity)

Answer 1

The elements in group 7 are: fluorine, chlorine, bromine, iodine and astatine.

Question 2

What are the properties of halogens?

Answer 2

They are non-metals, poisonous, each have seven electrons in their outermost shell, never found free in nature and are diatomic.

Question 3

What is meant by diatomic?

Answer 3

Diatomic means they form molecules made of pairs of atoms sharing electrons (forming a single covalent bond between the two halogen atoms).

Question 4

What is iodine?

Answer 4

Iodine is a dark grey solid that gives out purple vapour when heated.

Question 5

What is bromine?

Answer 5

Bromine is a red-brown liquid that gives out an orange vapour when heated.

Question 6

What is chlorine?

Answer 6

Chlorine is a green gas.

Question 7

What is astatine?

Answer 7

Astatine is a black solid.

Question 8

What is fluorine?

Answer 8

Fluorine is a pale yellow gas.

Question 9

What are the characteristics of fluorine?

Answer 9

Very reactive, poisonous gas

Question 10

What are the characteristics of chlorine?

Answer 10

Reactive, poisonous and dense gas

Question 11

What are the characteristics of bromine?

Answer 11

Dense volatile (easily evaporated) liquid

Question 12

What are the characteristics of Iodine?

Answer 12

Shimmery, crystalline solid that sublimes (solid that changes directly into vapour when heated) to form a purple vapour.

Question 13

Why do melting and boiling points of the halogens increase as you go down group 7?

Answer 13

This is due to increasing intermolecular forces as the atoms become larger, so more energy is required to overcome these forces

Question 14

Why do the physical state of the halogens changes as you go down the group?

Answer 14

This is due to the melting and boiling points increasing as you go down the group, because of the increasing intermolecular forces as the atoms become larger, meaning more energy is required to overcome these forces.

Question 15

What happens to the colour of halogens as you descend the group?

Answer 15

The colours of the halogens become darker as you descend the group.

Question 16

Chlorine, bromine and iodine react with metals and non-metals to form…

Answer 16

Compounds

Question 17

The halogens react with some metals to form…

Answer 17

Ionic compounds; metal halide salts

Question 18

What charge does the halide ion carry?

Answer 18

The halide ion carries a -1 charge.

Question 19

What happens to reactivity of halogens a you move down the group?

Answer 19

The halogens decrease in reactivity moving down the group.

Question 20

How does the position of the halogen affect the rate of the reaction?

Answer 20

The rate of reaction is slower for halogens which are further down the group (bromine and iodine).

Question 21

What structure do halogens form when they react with non-metals?

Answer 21

The halogens react with non-metals to form simple molecular covalent structures.

Question 22

What do the halogens react with hydrogen to form?

Answer 22

Hydrogen halides (e.g. hydrogen chloride)

Question 23

When do halogen displacement reactions occur?

Answer 23

A halogen displacement reaction occurs when a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide.

Question 24

What happens to the reactivity of the halogens as you descend the group?

Answer 24

The reactivity of group 7 elements decreases as you move down the group.

Question 25

If you add chlorine solution to colourless potassium bromide or potassium iodide solution, will a displacement reaction occur? And explain why. If yes, describe the colour change for both bromine and iodine.

Answer 25

Yes, a displacement reaction will occur; due to the fact chlorine is more reactive than both bromine and iodine. The solution becomes orange if bromine is formed or solution becomes brown if iodine is formed.

Question 26

If you add bromine to potassium iodide solution, will a displacement reaction occur? And explain why. If yes, describe the colour change for iodine.

Answer 26

Yes, a displacement reaction will occur as bromine is more reactive, it will displace the iodine from the aqueous solution of the Potassium iodide. A brown colour of iodine is seen.

Question 27

What is another name for displacement reactions?

Answer 27

Single replacement reactions

Question 28

What are halides?

Answer 28

Halides are what we refer to halogens when they gain an electron during reactions forming -1 ions (halide ions)

Question 29

What charge do halide ions have?

Answer 29

They have a -1 charge.

Question 30

Explain the trend in reactivity for group 7, in terms of electronic configuration.

Answer 30

As you go down group 7, the number of shells of electrons increases. However, halogen atoms form negative ions when they gain an electron to obtain a full outer shell, meaning that the increased distance from the outer shell to the nucleus as you go down a group makes the ability to attract an electron harder and therefore the halogens become less reactive.

Question 31

What is the symbol for Chlorine?

Answer 31

Cl2

Question 32

What is the symbol for Bromine?

Answer 32

Br2

Question 33

What is the symbol for Iodine?

Answer 33

I2

Question 34

What is the symbol for Astatine?

Answer 34

At2

Question 35

What is the symbol for Fluorine?

Answer 35

F2

Question 36

How does Chlorine react with the iron wool?

Answer 36

Iron wool burns and glows brightly.

Question 37

How does Bromine react with the iron wool?

Answer 37

Iron wool glows but less brightly than
with chlorine.

Question 38

How does Iodine react with the iron wool.

Answer 38

Iron wool has a very slight glow.

Question 39

Which experiment shows the reactivity of halogens?

Answer 39

The iron wool experiment

Question 40

What happens when halogens react with another substance?

Answer 40

They become negative ions (anions) and get a -1 charge. When this happens, we call them halides.