9.09.1 Group 0 - Noble Gases

Syllabus

The elements in Group 0 of the Periodic Table are called the Noble Gases.
They are unreactive and do not easily form molecules because their atoms have stable arrangements of electrons.
The noble gases have eight electrons in their outer shell, except for Helium, which has only two electrons.
The boiling points of noble gases increase with increasing relative atomic mass (down the group).

Students should be able to:

explain how properties of the elements in Grp 0 depend on the outer shell of electrons
predict properties from given trends down the group.

What does this mean?

What are Noble Gases?

Group 0 are known as the Noble Gases because they (almost) never react with any other elements.

We say they are chemically inert.

Other elements react because they need to gain/lose or share electrons in order to achieve a full outside shell (electronic stability).

But Noble Gases already have full outside shells He (2), Ne (2.8), Ar (2,8,8).

Because Noble gases have full outside shells their atoms don't even join up to make molecules in the way that Oxygen and Nitrogen form O2 and N2 molecules.

Noble gases are the only elements that exist as single atoms unattached to any other.

You may see these referred to as Group 0, Group 8 or Group 18.

They may also sometimes be called the Inert Gases and we, at one time, called the Rayleigh Gases after one of the men who discovered them.

Boiling Points

As you can see, the boiling point increases as we go down the group.

This means that the forces between the atoms must get stronger down the group too.

Why?

We don't need to know in detail but -- the bigger the atom, the more electrons it has and the stronger its forces.

Obviously, as we put more neutrons and protons into atoms they become heavier - so the density of the Noble gases increases down the group too.

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