The document discusses the properties and discovery of noble gases. It notes that: - Noble gases (group 0) are very unreactive due to their full outer electron shells. This stability makes them similar across the group. - Helium was first discovered on the sun in 1868. Argon was discovered in the 1890s after nitrogen from air was found to contain a small quantity of an inert element. - Ramsay realized argon needed its own group and later discovered it contained traces of other noble gases - neon, krypton, and xenon. Radon was discovered in 1900.

1. 3.3.1 Chem. Properties of groups
Chem. Properties of groups
•Discuss the similarities and differences
in the chemical properties of elements
in the same group

2. Where are the noble gases?
The elements in group 0, on the right of the periodic table,
are called the noble gases.
He helium
Ne neon
Ar argon
Kr krypton
Xe xenon
Rn radon

3. Discovery of argon
Because the noble gases are so unreactive, they were very
difficult to identify.
The first noble gas, helium, was discovered on the Sun in
1868 by William Ramsay and Morris Travers. It was not
known to exist on Earth until 1895.
In the early 1890s, a British physicist Lord Rayleigh found
that nitrogen obtained from the air was very slightly denser
than nitrogen obtained from decomposing ammonia.
He and his colleague William Ramsay
investigated this and found that the
nitrogen from the air contained a small
quantity of an inert element.
They finally managed to isolate the
element, which they called argon.

4. Discovery of argon
Ramsay realised that there was no place for this new gas in
the periodic table, and he predicted that it belonged to a
whole new group of elements.
He experimented on the argon with his colleague Morris
Travers, and in 1898, they discovered that the argon actually
contained tiny quantities of the three other noble gases,
neon, krypton and xenon.
Radon was discovered in 1900.

5. Why are they called the ‘noble gases’?
The noble gases all form colourless
gases at room temperature.
They are all very unreactive.
Noble gases were originally called
‘inert gases’, as they were thought
not to react with anything. Then in
1962, a British chemist, Neil Bartlett,
made a compound with xenon.
The name was changed to ‘noble gases’ as they were
considered similar to the very unreactive precious metals gold
and platinum, which are sometimes called ‘noble’ metals.
Now only neon and helium have not yet been made to form
compounds.

6. The noble gases
Why are the noble gases so unreactive?

7. How does electron structure affect reactivity?
All noble gases have full outer electron shells and do not need
to gain, lose or share electrons.
This means that: helium
 The noble gases are very 2
stable and the most
unreactive (or inert) of all the
elements. All of the noble neon
gases are similarly unreactive, 2,8
up and down the group.
 They do not normally form
bonds with other elements.
 They are monatomic, which argon
means they exist as 2,8,8
individual atoms. Most other
gases are diatomic.

8. Why is it called group 0?
Why is group 0 not called group 8, even though it comes after
group 7?
It used to be called group 8, and still is in some cases.
0
8
 In the rest of the periodic table, the number
He of the group is the same as the number of
Ne outer shell electrons in the elements of that
group.
Ar
 However, this is not true for the noble
Kr gases. Helium only has 2 electrons in its
outer shell, while the others all have 8.
Xe
 Because of this, the group’s number was
Rn changed to 0.