2.9 Group 7 & Group 0 (Halogens & Noble Gases)

Question 1

What type of elements is Group 7 made up of?

Answer 1

Non-metal elements like fluorine, chlorine, bromine, iodine, astatine

Question 2

In Group 7, the halogens exist as d________ m___________. Sharing one pair of electrons in a covalent bond gives both atoms a full outer shell.

Answer 2

diatomic molecules

Question 3

At room temperature, how does Fluorine act?

Answer 3

Fluorine is a highly reactive, toxic, pale yellow gas

Question 4

At room temperature and pressure, how does Chlorine act?

Answer 4

Chlorine is a fairly reactive, poisonous, green gas

Question 5

At room temperature and pressure, how does Bromine act?

Answer 5

Bromine is a poisonous, red-brown liquid, which gives off an orange vapour at room temperature

Question 6

At room temperature and pressure, how does Iodine act?

Answer 6

Iodine is a dark grey crystalline solid

Question 7

As you go down Group 7, does the melting and boiling points of each halogen increase or decrease? + why

Answer 7

Increase, this is because there’s an increase in the number of electrons in each atom as you go down the group. More electrons means there are greater intermolecular forces between the molecules, so more energy is needed to overcome them

Question 8

When you go down Group 7, why does reactivity decrease? (3)

Answer 8

• A halogen atom only needs to gain one electron to form a 1- ion with a stable electronic structure.
• The easier it is for a halogen atom to attract an electron, the more reactive the halogen will be
• As you go down group 7, it gets harder to attract he extra electron to fill the outer shell when its further away from the nucleus

Question 9

The halogens will react vigorously with alkali metals to form salts called ‘_____ ________”

Answer 9

metal halides

Question 10

Describe the noble gases in Group 0 (5)

Answer 10

• Group 0 elements are called the noble gases and include the elements helium, neon and argon etc.
• They all have 8 electrons in their outer energy level, apart from helium which has 2, giving them a full outer shell. As their outer shell is energetically stable they don’t need to give up or gain electrons to become more stable
• They exist as monatomic gases - single atoms not bonded together
• All elements in Group 0 are colourless gases at room temperature
• As the noble gases are inert they’re non-flammable - they won’t set on fire

Question 11

When you go down Group 0, do the melting and boiling points of the elements increase or decrease? + why

Answer 11

Increase - there’s an increase in the number of electrons in each atom leading to greater forces between the atoms which need to be overcome

Question 12

For halogen displacement reactions, what are the colour changes that take place for Halide salts, Bromine water, Chlorine water and Iodine water

Answer 12

• Halide salts (e.g. KCl, KBr, Kl)
• Bromine water is orange
• Chlorine water is colourless
• Iodine water is brown

Question 13

Are noble gases flammable?

Answer 13

No

Question 14

Why are the noble gases inert? (chemically unreactive)

Answer 14

The atoms have a full outer shell of electrons