1. IC4.7.4 Spectroscopy © Oxford University Press 2011 Spectroscopy LQ: How can spectroscopy be used to identify unknown elements in a compound?

2. IC4.7.4 Spectroscopy © Oxford University Press 2011 learning outcomes….. MUST: Recognise that elements have distinctive line spectrum (B) SHOULD: Identify unknown elements from line spectrum (A) COULD: Explain how spectroscopy has discovered new elements (A*)

3. IC4.7.4 Spectroscopy © Oxford University Press 2011 https://www.youtube.com/watch?v=1EXr_L7Ojqg https://www.youtube.com/watch?v=jJvS4uc4TbU

4. IC4.7.4 Spectroscopy © Oxford University Press 2011 Rainbows are spectra made as sunlight passes through raindrops. Sunlight splits up into the various colours of light it is made from.

5. IC4.7.4 Spectroscopy © Oxford University Press 2011 Isaac Newton passed white light through a prism. It split into the colours of the rainbow.

6. IC4.7.4 Spectroscopy © Oxford University Press 2011 All atoms give off light when heated, although sometimes this light is not visible to the human eye. Each element has its own distinctive line spectrum. This technique is known as spectroscopy. Some examples of what line spectra look like are shown here

7. IC4.7.4 Spectroscopy © Oxford University Press 2011

8. IC4.7.4 Spectroscopy © Oxford University Press 2011 Flame tests and line spectra Elements give off a characteristic colour in a flame test. A spectroscope allows that light to be analysed. Different elements have different line spectra. Sodium flame test Line spectrum of sodium.

9. IC4.7.4 Spectroscopy © Oxford University Press 2011

10. IC4.7.4 Spectroscopy © Oxford University Press 2011

11. IC4.7.4 Spectroscopy © Oxford University Press 2011

12. IC4.7.4 Spectroscopy © Oxford University Press 2011

13. IC4.7.4 Spectroscopy © Oxford University Press 2011 Scientists have used line spectra to discover new elements. In fact, the discovery of some elements, such as rubidium and caesium, was not possible until the development of spectroscopy

14. IC4.7.4 Spectroscopy © Oxford University Press 2011 Modern spectroscopy Modern spectroscopy is used in laboratories to identify unknown chemicals… …and in space to find out more about stars, planets and galaxies.

15. IC4.7.4 Spectroscopy © Oxford University Press 2011 1.When they are heated, some elements emit distinctive ____________, for example –lithium ____; –sodium ____________________; –potassium _____. 2.The light emitted from an element gives… 3.The study of spectra has helped chemists to… 4.The discovery of some elements depended on… C D Flame colours and spectra discover new elements (e.g. helium). the development of new practical techniques (for example spectroscopy). a characteristic line spectrum. flame colours red (street lamp) yellow lilac © Class Leading Ltd. 2013. Permission granted for non-commercial educational use provided that this copyright notice is included.

16. IC4.7.4 Spectroscopy © Oxford University Press 2011 Example on board 1.How can you tell that the unknown sample contains sodium? 2.How can you tell that the unknown sample does not contain potassium? 3.How can you tell that the unknown sample contains elements other than sodium?

17. IC4.7.4 Spectroscopy © Oxford University Press 2011

18. IC4.7.4 Spectroscopy © Oxford University Press 2011

19. IC4.7.4 Spectroscopy © Oxford University Press 2011

20. IC4.7.4 Spectroscopy © Oxford University Press 2011

21. IC4.7.4 Spectroscopy © Oxford University Press 2011

22. IC4.7.4 Spectroscopy © Oxford University Press 2011