1. Lecture 2310/28/05

2. Quiz 1. What does the quantum number “l” represent? 2. Calculate the wavelength of light emitted when an electron changes from n = 3 to n = 1 in the H atom?

3. m l  orbital -l... 0... +l  orientation Summary: Quantum numbers n  shell1, 2, 3, 4,...  size and energy l  subshell0, 1, 2,... n – 1  shape m s  electron spin+1/2 and -1/2  spin

4. Pauli Exclusion Principle No two electrons can have the same set of the four quantum numbers (n, l, m l, m s )

6. Writing Atomic Electron Configurations 1 1 s value of n value of l no. of electrons spdf notation for H, atomic number = 1 Two ways of writing configurations spdf notation Two ways of writing configurations spdf notation

7. Writing Atomic Electron Configurations Two ways of writing configurations orbital box notation. Two ways of writing configurations orbital box notation. One electron has n = 1, l = 0, m l = 0, m s = + 1/2 Other electron has n = 1, l = 0, m l = 0, m s = - 1/2

8. Aufbau principle Electrons are added from lowest to highest energy Single electron atom (Bohr) Energy related to n Multi-electron atom Energy related to n + l

9. See “Toolbox” for Electron Configuration tool.

12. LithiumLithium Group 1A Atomic number = 3 1s 2 2s 1 ---> 3 total electrons

13. BoronBoron Group 3A Atomic number = 5 1s 2 2s 2 2p 1 ---> 5 total electrons 5 total electrons

14. CarbonCarbon Group 4A Atomic number = 6 1s 2 2s 2 2p 2 ---> 6 total electrons 6 total electrons HUND’S RULE When placing electrons in a set of orbitals having the same energy, fill each with a single electron first

15. OxygenOxygen Group 6A Atomic number = 8 1s 2 2s 2 2p 4 ---> 8 total electrons