Unit 25 The Noble Gases, Their Properties And Uses

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Unit 25

The Noble Gases, their Properties and Uses

Science Interactive LTD Copyright 2005 Fluorine Bromine Iodine 9P + 10N 9E - Chlorine 17P + 18N 17E - 35P + 45N 35E - 53P + 74N 53E - F Cl Br I 9 17 35 53 19 35 80 127 Helium Neon Krypton 2P + 2N Argon 18P + 22N 10P + 10N 36P + 48N He Ne Ar Kr 2 10 18 36 4 20 40 84 36E - 10E - 2E - 18E -

That group VIII elements are called the Noble gases.

The physical and chemical properties of group VIII elements, the Noble gases.

That they have similar chemical and physical properties based on their electronic configuration.

That because of their full outer shells, the Noble gases do not form compounds with other metal or non metal elements.

Understand that their discovery in the atmosphere was hampered by their stability.

Some of the main uses of the Noble gases.

Elements, Noble, Gases, Unreactive, Electrons, Physical, Properties, Inert, Monatomic, Helium, Neon, Argon & Krypton. Unit 25: The Noble Gases, their Properties and Uses web: www.science-interactive.co.uk email: sales@science-interactive.co.uk Science Interactive LTD PO BOX 50764 LONDON NW6 9AT Click mouse to begin Science Interactive LTD Copyright 2005 Understand: Keywords:

Physical properties of the Noble gases one Group VIII of the periodic table contains a family of very stable non-metals known as the Noble gases. This group contains h________, neon, argon and krypton. They are all monatomic colourless gases . All but helium are found in low quantities in our atmosphere. Helium is found trapped under the bedrock along with deposits of n_________ gas. Helium is so light that the Earth’s gravity is not strong enough to keep it in our atmosphere. Eventually we will run out of helium as it escapes the Earth’s gravitational pull. Give two uses helium and neon ? The Noble gases: Science Interactive LTD Copyright 2005 Word bank: helium natural The Noble gases have similar chemical and physical properties because they all have eight electrons in their outer shell. They are all colourless monatomic gases which do not form ionic or covalent compounds with any other elements. They also have extremely low melting and boiling points. The Noble gases Notes Diagram Found in group VIII of the periodic table, all the Noble gases have eight electrons in their outermost electron shell. They all therefore have a full outer shell. This is what makes them very stable monatomic gases. Position of the Noble gases

Physical properties of the Noble gases two The group VIII elements, the Noble gases are all colourless gases unable to form ionic and c_______ compounds with other elements. They have similar physical and chemical properties. They are all monatomic gases. They have extremely low melting and boiling points which increase slightly as you descend the group. Although they are very s______ they do have many important uses. Why is helium used in airships rather than hydrogen which provides more lift ? Physical properties of group VIII Noble gases: Colourless He Ne Ar Kr Colourless Colourless Colourless 2 2,8 2,8,8 2,8,18,8 Science Interactive LTD Copyright 2005 Word bank: covalent stable -179 o C -189 o C -210 o C -272 o C Melting point Gas Krypton Gas Argon Electron configuration Formula Colour Gas Gas State at room temperature Neon Helium Element Symbol

The discovery of the Noble gases The noble gases were not discovered until about the turn of the last century. Because the Noble gases are highly un-reactive, they remained hidden in the a____. Helium was discovered with deposits of natural gas found under the bedrock. In 1892, scientists discovered that, when all the nitrogen and oxygen from a sample of air was reacted with hot magnesium, there was around one percent of the gas that would not react. This small fraction contained n______, argon and krypton. Discovery of the Noble gases: 100 50 0 Nitrogen Oxygen Noble gases CO 2 Science Interactive LTD Copyright 2005 Word bank: air neon Hydrogen although having greater lift has now been replaced by stable helium. Using helium The Noble gases were not discovered until 1892 due to their stability. They make up only 1% percent of the atmosphere. Although they are stable they are still useful. Percentage composition of noble gases in air Notes Diagram

Helium and its uses Helium is the least dense of the Noble gases. A balloon full of helium will have lift in normal air. Although hydrogen gives more l_____ because it has the lowest density of any of the elements it is also highly reactive. Helium makes for a safe alternative and is used in airships and ‘party balloons’ Helium is also used by deep seas divers instead of nitrogen. It has a low solubility and therefore reduces the risk of divers suffering the bends. This is when nitrogen in the blood comes out of solution and begins to bubble in the b_______. This can be fatal. Why is this condition called the bends ! Helium and its uses: Science Interactive LTD Copyright 2005 Word bank: lift bubble Helium is also used for party balloons. They are able to rise above the air. They also (when breathed in) make you sound like Mickey Mouse. Helium balloons Notes Diagram Helium Helium is a low density stable gas that gives ‘lift’ to objects like balloons in air. Hydrogen is better but it is also very unstable and can react with the oxygen in the atmosphere forming water. This is an explosive reaction. Using helium for lift

Neon and its uses Neon is the most widely used Noble gas. Neon is used to make fluorescent light tubes, which can take on many colours. When you pass a high v_______ current across a tube full of n______, it glows and gives off light. The tubes can be coloured using various dyes making them ideal for use in advertising signs around the World. If you take a trip to London’s Piccadilly Circus, then you will see hundreds of flashing neon signs all advertising various products and fast food companies. Explain why a neon light uses less energy than a normal filament bulb ? Neon and its uses: Science Interactive LTD Copyright 2005 Word bank: voltage neon By colouring the glass tube you can colour the light that is emitted. Neon lights do not produce any heat and are therefore much more efficient. Choose a colour Notes Diagram Neon Scientists found out that when you pass a high voltage current through a tube filled with neon, it fluoresces. Neon lights are used in advertising signs. There are also more energy efficient compared to filament bubs. Neon lights at Piccadilly circus

Argon and its uses Argon makes up nearly one percent of the composition of atmospheric air. Argon is more dense than air, so balloons filled with just argon appear to ‘sink.’ Argon has two main uses. Argon is used to replace air or o________ where you need an oxygen free environment in order to prevent combustion. Filament b______ made from tungsten contain argon to prevent the tungsten from oxidising with oxygen. Argon is also used during the welding of metals to prevent metals combusting with oxygen. What other processes require an oxygen free environment ? Argon and its uses: Science Interactive LTD Copyright 2005 Word bank: oxygen bulbs Light bulbs are filled with inert argon gas so that the tungsten filament does not begin to form tungsten oxide with oxygen from the atmosphere. Light bulbs Notes Diagram Argon During welding very high temperatures would cause most metals to begin to react with oxygen found in air. Argon is flowed over the weld to prevent the metals reacting. This techniques is called ‘argon welding’ Using argon during welding

Krypton and its uses Krypton makes up a very small fraction of the composition of atmospheric air. Like argon, krypton is more d______ than air. Krypton has one main use. Krypton is used to produce high energy lasers. These lasers are seen in disco lighting shows. They also carry sufficient energy to melt metal during their w________. When a high voltage current is applied to the krypton gas, a high energy light is emitted that is used to produce laser light. Find out from google.co.uk how laser light is produced ? Krypton and its uses: Science Interactive LTD Copyright 2005 Word bank: dense melting Krypton lasers are use to remove excess corneal tissue during laser eye correction. The cornea is reshaped to give the correct focal length. Eye surgery Notes Diagram Krypton Krypton is used in lasers used for disco lighting and welding. A high voltage current is applied to the krypton gas which produces a high energy beam. This energy is sufficient to cause melting in metals during welding. Krypton lasers

1: Define the following terms: Elements, Reactivity, Noble Gases, Inert, Ionic and Covalent. 2: Look at the three pictures below. Complete the table. 3: Answer the following using the following table: a) How much (percent) do the noble gases make up of the atmosphere. b) This gas was used to give lift to air ships. c) Argon is used in this device to stop the filament from combusting with oxygen. d) Whereas, the halogens are diatomic gases, the noble gases are what type of gas. e) All noble gases are said to be chemically what. Extension questions and homework Science Interactive LTD Copyright 2005 Properties and uses Helium Three Neon Two Krypton One Element Picture Lasers Sign Hydrogen Light bulbs Lift Reactive Diatomic One percent Monatomic Inert

4: Complete the following table. 5: Answer the following questions: a) What would happen when a light bulb is switched on and it is filled with normal air. b) Airships are no longer filled with, hydrogen. Helium is now used. Explain why. c) Explain why there are no known compounds that contain either helium, neon, argon or krypton. d) Why do helium balloons deflate more quickly than balloons filled with atmospheric air. e) How many electrons do (i) group I alkaline metals have in their outer shell (ii) The group VIII noble gases. f) Explain why the melting and boiling points of the nobles gases increases as you descent the group. 6: Look at the information in the table opposite: a) Why were the noble gases discovered very late and why do they have similar properties. b) Why is neon used in advertising signs. c) Why will we eventually rum out of the element helium. d) Why is argon used to replace air in light bulbs. e) Give two uses of a krypton laser. Internet: Go to google.co.uk and find out the ‘Hindenburg disaster’ where hydrogen, not helium was used as a lifting gas for this airship. Science Interactive LTD Copyright 2005 Kr Krypton colourless Argon Gas Neon 2 Helium Symbol Colour State at room temperature Electrons in outer shell Gas 1669 Phosphorus 1774 Oxygen 1898 Neon 1895 Helium < 2000 B.C Gold When found Element