1. Chemical Ideas 6.2 What happens when radiation intracts with matter?

2. c = λ ν c νλ c = speed of light = 3.00 x 10 8 m s -1 λ = wavelength m lambda ν = frequency Hz ( or s -1 ) nu Use m for λ

3. c = λν problems…. 1. Work out λ if v = 8.19 x 10 13 Hz c = 3.00x10 8 m s -1

4. Rearranging again…. E h

5. E = hν problems … h = 6.63 x 10-34 J Hz -1 Planck constant 2. If the frequency is 3.5 x 10 13 Hz, what is the energy of each photon? 3. If E = 4.6 x 10 -17 J per photon, what is the frequency (ν) of the radiation?

6. visibleultra violet E increases

7. What happens to electrons? 1 2 3 4 Electrons absorb energy Electrons are excited Electrons move to higher energy level E = h v

8. Molecules are made of more than one atom but they still have electrons. Electronic transitions Vis + UV

9. Molecules move !

10. There are vibrational energy levels as well as electronic energy level.. I.R.

11. There are rotational energy levels as well as electronic energy level.. microwave

12. Electronic transitions Vis + UV Rotational transitions Vibrational transitions Microwave I.R.

13. Note the range in Table 1, P130 Change..ΔE in joulesPart of e.m.s. in vibrational energy level 1 x 10 -20 to 1 x 10 -19 infrared C-F C-Cl C-Br

14. What could happen to a Cl 2 molecule in the Atmosphere? Visible U.V. Photodissociation radicals Electronic transitions U.V. + Ionisation

15. Now … Read CI 6.2 for yourself Complete Notes 3, 4 and 5 Try Q1, 2 and 4 from CI 6.2. Only do Q4 if you are doing AS maths!