Group 18: Noble gases

Group 18: Noble gases

Lessons

In this lesson, we will learn:
  • To recall the properties of noble gases.
  • To understand some of the uses of the noble gases.
  • To apply understanding of electronic structure to explain the properties of the noble gases.

Notes:

  • We have seen that the Periodic Table is arranged, top-left to bottom-right, by proton number and number of outer shell electrons. The number of outer shell electrons dictates the chemical properties of an element.
    Therefore, you can see which elements have similar properties – they will be in the same column of the table as each other - the columns which we call groups.

  • The noble gases are another group of well-studied elements in the periodic table with a specific set of properties that make them unique. They are in group 8 (18 if you include transition metals), the right-most column of the table.

  • The noble gases have the following properties:
    • They are colorless, odorless gases.
    • They are very unreactive – this is the most important fact to know about noble gases. It is the main reason the whole group of noble gases were discovered very late (after Mendeleev had developed the Periodic Table). Being gases with no color or smell humans could sense, and no reactions with anything around them to study, chemists could not prove they were there!
    • Noble gases exist as single, monatomic atoms.
    • They are non-metals and are therefore very poor conductors of electricity.

  • There is not much change in the properties of noble gases going down the group, however their melting and boiling point does slightly increase – however all of them are still well below zero degrees Celsius. The density of the noble gases also increases going down the group.

  • Despite their unreactive nature they have a few important uses:
    • Helium is used in hot air balloons and air ships. Objects filled with helium float because helium isn't as dense as air. It is also used in air containers for deep sea divers. At high underwater pressure, too much nitrogen and oxygen gets into the blood causing toxic side effects. Because it is inert, if some air in the containers is replaced by helium, it keeps the container pressurized, and the helium has no side effects on the divers because it is inert!
    • Neon is used in signs – if an electric current is ran through a glass tube with neon in it, the gas will start glowing.
    • Argon is used in small quantities to protect light bulb filaments – the very hot filament metal burns in oxygen but not in argon.
  • Introduction
    Noble gases: A summary
    a)
    History of the noble gases.

    b)
    Properties of the noble gases.

    c)
    Uses of the noble gases.


  • 1.
    Apply your knowledge of types of bonding to explain the properties of the noble gases.
    Explain why the noble gases have such a low melting and boiling point compared to other groups in the Periodic Table.

  • 2.
    Apply your knowledge of types of bonding to explain trends in the properties of the noble gases.
    Explain using ideas of intermolecular forces (Intermolecular forces lesson), why the melting and boiling point of the noble gases increases going down the group.