Group 7 (Halogens)

Question 1

What are the elements in group 7 called?

Answer 1

The Halogens

Question 2

How many electrons do they all have in their outer shell and what does having the same number of electrons mean?

Answer 2

They have 7 electrons in their outer shell, and since they all have this same number of electrons, they share similar properties

Question 3

What state and appearance is fluorine at room temperature?

Answer 3

Yellow gas

Question 4

What state and appearance is chlorine at room temperature and in solution?

Answer 4

• Yellow/green gas
• Pale green in solution

Question 5

What state and appearance is bromine at room temperature and in solution?

Answer 5

• Red/brown liquid
• Orange in solution

Question 6

What state and appearance is iodine at room temperature and in solution?

Answer 6

• Grey/black solid
• Dark brown in solution

Question 7

What are trends in physical properties of these elements?

Answer 7

• They are all poisonous
• They are reactive, but decrease in reactivity as you move down the group

Question 8

What happens to the meling and boiling points of the halogens as you move down the group and why?

Answer 8

They increase, this is because the atoms become larger and there are stronger intermolecular forces

Question 9

What happens when a halogen reacts with a metal?

Answer 9

An ionic compound which is a halide salt is formed (halide compound, eg. sodium chloride)

A halide is a ionic compound contaning a halogen

Question 10

What happens when a halogen reacts with a non-metal?

Answer 10

Simple covalent structures are formed, such as hydrogen chloride

Question 11

What happens in halogen displacement reactions?

We only need to know ones concerning chlorine, bromine and iodine

Answer 11

• A more reactive halogen displaces a less reactive halogen
• For example, Chlorine + Potassium Bromide = Potassium Chloride + Bromine
• If it is not more reactive, nothing will happen

Remember that the elements get less reactive as you go down the group, unlike group 1 metals

Question 12

In terms of electronic configuration, why does the reactivity of group 7 elements decrease as you move down the group?

Answer 12

• The further down in the group, the more electron shells each element has
• The less electron shells you have, the closer the outer shell of electrons will be to the nucleus
• Since these elements are trying to attract an electron, the closer the outer shell of the atom is to the nucleus, the stronger forces of attraction there will be to electrons
• This makes them more reactive

The alkaline metals try lose an electron, so the more shells means more reactive, but halogens are trying to gain an electron, so more shells means less reactive