Presentation is loading. Please wait.

Presentation is loading. Please wait.

© Boardworks Ltd 2005 1 of 24 KS4 Chemistry Noble Gases.

Similar presentations


Presentation on theme: "© Boardworks Ltd 2005 1 of 24 KS4 Chemistry Noble Gases."— Presentation transcript:

1 © Boardworks Ltd of 24 KS4 Chemistry Noble Gases

2 © Boardworks Ltd of 24 Noble Gases Physical properties Uses Discovery and electron structure Summary activities Contents

3 © Boardworks Ltd of 24 FrRaAcRfDbSgBhHsMtDsRg??????? CsBaLaHfTaWReOsIrPtAuHgTlPbBiPoAt RbSrYZrNbMoTcRuRhPdAgCdInSnSbTeI KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBr NaMgAlSiPSCl LiBeBCNOF 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

4 © Boardworks Ltd of 24 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 He had passed a series of electric sparks through a mixture of air and oxygen, and collected the gases that were produced.

5 © Boardworks Ltd of 24 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 predicted that 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.

6 © Boardworks Ltd of 24 The noble gases Why are noble gases so unreactive?

7 © Boardworks Ltd of 24 helium 2 neon 2,8 argon 2,8,8 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 are diatomic. This means that:

8 © Boardworks Ltd of 24 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 groups number was changed to 0 because of this. RnXeKrArNeHe 0 It used to be called group 8, and still is in some cases.

9 © Boardworks Ltd of 24 Noble Gases Physical properties Uses Summary activities Contents Discovery and electron structure

10 © Boardworks Ltd of 24 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.

11 © Boardworks Ltd of 24 Patterns: density

12 © Boardworks Ltd of 24 Comparing the density of noble gases

13 © Boardworks Ltd of 24 Patterns: boiling point

14 © Boardworks Ltd of 24 Noble Gases Physical properties Uses Summary activities Contents Discovery and electron structure

15 © Boardworks Ltd of 24 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.

16 © Boardworks Ltd of 24 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-performance magnets, e.g. in body scanners, because it has a very low boiling point (-269 °C).

17 © Boardworks Ltd of 24 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).

18 © Boardworks Ltd of 24 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.

19 © Boardworks Ltd of 24 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.

20 © Boardworks Ltd of 24 True or false?

21 © Boardworks Ltd of 24 Noble Gases Physical properties Uses Summary activities Contents Discovery and electron structure

22 © Boardworks Ltd of 24 Glossary density – A measure of mass in a given volume. Often expressed in g/dm 3. 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.

23 © Boardworks Ltd of 24 Anagrams

24 © Boardworks Ltd of 24 Multiple-choice quiz


Download ppt "© Boardworks Ltd 2005 1 of 24 KS4 Chemistry Noble Gases."

Similar presentations


Ads by Google