Core Knowledge – Topic 6

1) What do we call group 1, group 7 and group 0 in the periodic table?

Answer 1
The alkali metals, the halogens and the noble gases.

2) In terms of electronic configuration, what do all the elements in:

  1. Group 1 have in common?
  2. Group 7 have in common?
  3. Group 0 have in common?
Answer 2

They have:

  1. 1 electron on their outer shell
  2. 1 electron is needed to complete their outer shell.
  3. A full outer shell of electrons.

3) How are the alkali metals different from transition metals?

Answer 3

  1. They are soft (can be cut with a knife).
  2. They have comparatively low melting points.

4) Describe the reaction of sodium with water.

Answer 4

  1. The metal reacts and moves around the surface of the water.
  2. The reaction gives off a gas.
  3. The product of the reaction is soluble in the water.

5) What two products are formed when alkali metals are added to water?

Answer 5
A hydroxide and hydrogen gas.

6) State the order of reactivity in group one and explain it.

Answer 6
Reactivity increases as you go down the group. This is because the outer electron is further away from the nucleus and is therefore more easily lost.

7) What are the colours and physical states of the halogens at room temperature?

Answer 7
Fluorine is a pale yellow gas. Chlorine is a yellow/green gas. Bromine is a brown liquid. Iodine is a grey solid.

8) What is the pattern in:

  1. Boiling point
  2. Colour intensity
  3. Reactivity

As you go down the halogen group?

Answer 8

  1. Boiling point increases
  2. Colour intensity increases
  3. Reactivity decreases

9) What is the test for chlorine?

Answer 9
Chlorine turns damp litmus paper red and then bleaches it.

10) What is formed when halogens react with hydrogen?

Answer 10
Hydrogen halides. These can dissolve in water to from acids e.g. HCl, hydrogen chloride dissolves in water to form hydrochloric acid.

11) What is formed when halogens react with metals?

Answer 11
Metal halides. E.g. 2Fe + 3Cl2 = 2FeCl3 (iron(III)chloride)

12) State the order of reactivity of the halogens and explain it.

Answer 12
Reactivity decreases as you go down the group.

13) If chlorine is added to sodium bromide solution what happens?

Answer 13
A displacement reaction takes place forming sodium chloride solution and bromine. This is because the chlorine is more reactive than the bromine.

14) When chlorine reacts with sodium bromide what type of reaction is it?

Answer 14
Displacement reaction which is a redox reaction.

15) When chlorine reacts with sodium bromide, what is oxidised and what is reduced? Explain your answer in terms of electrons.

Answer 15
The chlorine will gain electrons and therefore be reduced.The bromide ion will lose electrons and is therefore oxidised.

16) Why do the halogens become less reactive as you go down the group?

Answer 16
The halogens all need to gain an electron to complete their outer shells. The positive nucleus attracts the electron the halogens need to fill the outer shell. The halogens at the top of the group have less shells so the attractive force of the nucleus is much stronger as the gap is closer which makes them more reactive.

17) Why are the noble gases unreactive?

Answer 17
They already have a full outer shell of electrons.

18) What are the properties of the noble gases?

Answer 18

  1. Inertness (so used in welding and filament lamps).
  2. Low density (used in balloons).
  3. non-flammability.

19) What is the trend in density and boiling point as you go down the noble gas group?

Answer 19
Both the densities and the boiling points of the noble gases increase as you go down the group.