1. Ground state E1E1 E2E2 E3E3 E4E4 E5E5 Energy levels continue to get closer until they finally converge at..... E  THE HYDROGEN ATOM NUCLEUS ELECTRON The “Ground State” is the lowest energy level available to the electron. Other energy levels may be added as follows: [CLICK]

2. E2E2 [CLICK FOR ELECTRON TO OCCUPY HIGHER LEVELS]

3. E3E3

4. E4E4

5. E5E5

6. Electron has been excited to just beyond   [CLICK TO CONTINUE]

7. When the H atom receives enough energy for the electron to be excited to just beyond the outermost energy level, E , it is said to be “ionised”. This is represented by the equation: H (g) H + (g) + e -  H = IONISATION ENTHALPY In order to determine the value of  H for this process the LYMAN series of the atomic emission spectrum must be examined which lies in the UV region. This arises as follows:

8. 2.4 2.6 2.8 3.0 3.2 Frequency/ 10 15 Hz LYMAN SERIES As the electron falls from higher to lower energy level, E 2 to E 1,, so a photon of light is emitted with frequency, v, given by the equation :  E = E 2 - E 1 = h X v [ where h is Plank’s constant with the value of 6.63 X 10 -34 JHz -1 ] 1 2 3 4 5

9. 2.4 2.6 2.8 3.0 3.2 Frequency/ 10 15 Hz LYMAN SERIES

10. 2.4 2.6 2.8 3.0 3.2 Frequency/ 10 15 Hz LYMAN SERIES

11. Frequency/ 10 15 Hz 2.4 2.6 2.8 3.0 3.2 LYMAN SERIES

12. 2.4 2.6 2.8 3.0 3.2 Frequency/ 10 15 Hz This energy drop,  E = E  - E 1, is the identical value to the energy required to ionise the atom. LYMAN SERIES

13. 2.4 2.6 2.8 3.0 3.2 Frequency/ 10 15 Hz The frequency at the convergence limit is 3.27 x 10 15 Hz LYMAN SERIES The ionisation enthalpy,  H = h X v =6.63x10 -34 x 3.27x10 15 =2.17 x10 -18 joules Now express this in kJ mol -1

14. THE END