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KS4 Chemistry

Noble Gases

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Noble Gases

Physical properties

Uses

Discovery and electron structure

Summary activities

Contents

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Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ? ? ? ? ? ? ?

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br

Na Mg Al Si P S Cl

Li Be B C N O F

H

Rn

Xe

Kr

Ar

Ne

He

Group 0 – the noble gases

Noble gases are in group 0 of the periodic table, on the right.

Rn

Xe

Kr

Ar

Ne

He

0

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The noble gases were discovered and isolated in the 1890s by William Ramsey, Lord Rayleigh, and Morris Travers.

Discovery of argon

Each time he did the experiment, around 1% of the gas mixture did not react.

Ramsay and his colleagues did further experiments and finally isolated a new element, which they called argon, from the Greek ‘argos’ meaning lazy or inactive.

Noble gases had actually been first discovered, but not recognized, by Henry Cavendish in 1766. He had passed a series of electric sparks through a mixture of air and oxygen, and collected the gases that were produced.

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Discovery of the other noble gases

Once Ramsay had discovered argon, he realised that there was no place in the periodic table for it to fit. He predictedthat argon belonged to a whole new group of elements.

In 1885 Ramsay identified helium, and in 1888 he identified neon, krypton and xenon after studying liquid air.

Radon was discovered in 1900.

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The noble gases

Why are noble gases so unreactive?

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helium2

neon2,8

argon2,8,8

Electron structure and reactivity

They do not normally form bonds with other elements.

All noble gases have full outer electron shells and do not need to gain, lose or share electrons.

They are very stable and the most unreactive (or inert) of all the elements.

They are monatomic, which means they exist as individual atoms. Most other gases arediatomic.

This means that:

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8

Group 8 becomes group 0

Why is group 0 not called group 8, even though it comes after group 7?

In the rest of the periodic table, the number of the group is the same as the number of outer shell electrons in the elements of that group.

However, this is not true for the noble gases. Helium only has 2 electrons in its outer shell, while the others all have 8. The group’s number was changed to 0 because of this.

Rn

Xe

Kr

Ar

Ne

He

0

It used to be called group 8, and still is in some cases.

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Noble Gases

Physical properties

Uses

Summary activities

Contents

Discovery and electron structure

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General properties of noble gases

All noble gases are colourless, odourless and unreactive. This makes them difficult to isolate and identify.

Because noble gases are so unreactive, there are few patterns, or trends, among the group.

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Patterns: density

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Comparing the density of noble gases

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Patterns: boiling point

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Noble Gases

Physical properties

Uses

Summary activities

Contents

Discovery and electron structure

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Uses of noble gases

Although noble gases are unreactive, they are still very useful elements.

Many uses of noble gases depend on their ability to prevent other, undesirable, reactions taking place.

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Uses of helium

The gas for inflating balloons and airships, because it is less dense than air and inflammable.

A protective gas for growing silicon crystals in silicon chip manufacture, because it is unreactive.

A component of breathing gas (with oxygen) for deep-sea divers, because it is unreactive, insoluble and prevents divers getting ‘the bends’.

Helium is used as:

A super-coolant for high-performancemagnets, e.g. in body scanners, because it has a verylow boiling point (-269 °C).

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Uses of neon

Neon is used:

In ‘neon’ advertising signs, because it glows red when an electric current is passed through it.

In TV tubes.

In certain types of lasers.

As a cryogenic refrigerant (when liquid).

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Uses of argon

Argon is used:

In normal light bulbs, because it is unreactive and prevents the tungsten filament from burning.

In energy-efficient fluorescent light bulbs.

As a ‘gas blanket’ for arc welding, because it is unreactive and prevents the hot welding metal from oxidizing.

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Uses of other noble gases

Krypton is used:

In lasers for eye surgery, to stop bleeding on the retina.

In lighthouses and other types of lamps.

In various types of electron tubes, lamps and lasers.

Xenon is used:

Radon is used:

To treat cancer by radiotherapy, because it is radioactive.

However, because radon is radioactive, it is also an environmental hazard.

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True or false?

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Noble Gases

Physical properties

Uses

Summary activities

Contents

Discovery and electron structure

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Glossary

density – A measure of mass in a given volume. Often expressed in g/dm3.

inert – Describes a substance that is unreactive under normal conditions.

monoatomic – An element that exists as a single atom.

noble gas – An element belonging to group 0 of the periodic table.

trend – A gradual change in a property or characteristic of elements in the same group of the periodic table.

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Anagrams

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Multiple-choice quiz