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PERIODIC TABLE OF ELEMENTS

Learn about the physical properties, unreactive nature, and various uses of noble gases such as helium, neon, argon, krypton, xenon, and radon. Discover how they are used in electron tubes.

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PERIODIC TABLE OF ELEMENTS

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  1. PERIODIC TABLE OF ELEMENTS Group 18 4S1 Monday, 15/4/2011 10.45 – 11.55 am

  2. Members of Noble Gases Helium Neon Argon Krypton Xenon Radon

  3. Physical Properties • Atomic radius (atomic size) • - increases down the group • - bcoz number of shells • occupied with electrons • increases down the group

  4. 2. Low mp & bp - bcoz noble gases are made up of single atoms (monoatomic) - the atoms are held together by weak van der Waals force of attraction -only small amount of E is needed to overcome the forces of attraction during melting & boiling

  5. 3. Mp & bp increases down the group - bcoz atomic size increases down the group. - thus, van der Waals forces of attraction btwn atoms of noble gases become stronger - more E is needed to overcome the stronger forces of attraction during melting & boiling

  6. 4. Low density - however, density increases slowly down the group - bcoz increase in mass is bigger compared to increase in volume when going down the group

  7. Unreactive properties of noble gases Duplet arrangement Octet arrangement

  8. (Cont.) Unreactive properties of noble gases • due to duplet & octet arrangement, noble gases are very stable • do not release e-, accept or share e- among each other or with other atoms • noble gases exist as monoatoms • Noble gases are chemically inert or • chemically unreactive

  9. Uses of Group 18 elements • Helium • - fill weather balloons & airships • - mixture of 80% He & 20% O2 is used • by divers as artificial atm (bcoz He is • less soluble in the blood compared to • N2 can cause decompression • sickness = bends) • - used in thermometer to measure • very low temp.

  10. Airship

  11. 2. Neon - fill advertising light bulbs, colour: reddish- orange - used as indicator light in small neon lamp  indicate circuit is on

  12. 3. Argon - fill electric bulbs - supply inert atm for welding at high temp. - carrier gas in liquid-gas chromatography

  13. Liquid-gas chromatography

  14. 4. Krypton - fill high speed photographic flash lamps - in lasers to repair retina of the eye

  15. 4. Xenon - used in electron tubes & spectroscopic lamps - used in bubble chambers 5. Radon - used in the treatment of cancer bcoz it is radioactive

  16. Electron tubes

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