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Group 0: the noble gasesIB MYP Chemistry: Revision notes

Section 1

What are the noble gases?

Group 0 is the last column of the periodic table. It contains helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn). They are colourless gases at room temperature and exist as single atoms (they are monatomic).

Key termsnoble gasmonatomic

Section 2

Why are they unreactive?

Noble gas atoms have a full outer shell of electrons:

  • helium has 2 electrons (its first shell is full)
  • all the others have 8 outer electrons

Because the outer shell is full, the atoms have no tendency to lose, gain or share electrons. They do not form ions or bonds with other elements, so they are unreactive (also called inert).

Key termsfull outer shellinert
Exam tip

Always link unreactivity to the full outer shell. Do not say 'they are stable' alone.

Section 3

Boiling points

The boiling points increase down the group:

  • helium −269 °C
  • neon −246 °C
  • argon −186 °C
  • krypton −153 °C
  • xenon −108 °C

The atoms get larger down the group, so the forces between them get stronger and more energy is needed to separate them.

You can use the trend to predict: radon, below xenon, boils at a higher temperature than xenon.

Key termsboiling point trend
Common mistake

Group 0 is not the same as Groups 1 and 7. There is no reactivity trend to learn, because none of them react. The trend to learn is the boiling point.

Section 4

Uses of helium, neon and argon

Uses follow from the properties:

  • Helium: less dense than air and non-flammable, so it fills balloons and airships (safer than hydrogen). Its very low boiling point makes liquid helium a coolant for MRI scanners.
  • Neon: glows red-orange when electricity passes through it, so it is used in advertising signs.
  • Argon: unreactive, so it fills filament light bulbs (stopping the hot filament burning) and gives a protective atmosphere for welding.
Key termsairshipfilament

Section 5

Applying the ideas: worked example

Question: Why is argon used in light bulbs instead of air?

  1. A filament gets extremely hot.
  2. Air contains oxygen, which would react with the hot filament and make it burn away.
  3. Argon has a full outer shell, so it is unreactive and does not react with the filament.

Answer: argon is unreactive because it has a full outer shell, so the filament does not burn.

Key termsprotective atmosphere

That's the notes covered.

Carry on to the next subtopic.

Exam questions on Group 0: the noble gases

  1. A party shop in Dubai fills foil balloons with helium. The balloons float upwards when released, and the shop owner has been told that helium is much safer to use than hydrogen.
    Explain why helium is safer than hydrogen for filling balloons.2 marks
  2. A welder in a workshop in Seoul joins two stainless steel plates using a very hot electric arc. A steady stream of argon gas is blown over the hot metal while the welding is done.
    Explain why argon is used instead of air during welding.2 marks
  3. The boiling points of the first five noble gases are: helium −269 °C, neon −246 °C, argon −186 °C, krypton −153 °C and xenon −108 °C. A student is asked to predict the properties of radon, the next noble gas below xenon. Room temperature is 20 °C.
    Describe the trend in boiling point down the group.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).