1 Electron Configuration Na: 1s 2 2s 2 2p 6 3s 1 Na: [Ne] 3s 1 classroom.sdmesa.edu/ssaidane/Docs%20.../ElectronConfiguration.ppt

2 Electron configurations tells us in which orbitals the electrons for an element are located. Three rules: –electrons fill orbitals starting with lowest energy level and moving upwards(Aufbau Principle); –no two electrons can fill one orbital with the same spin (Pauli Exclusion Principle); –For orbitals in the same sublevel, electrons fill each orbital singly before any orbital gets a second electron (Hund’s Rule). Electron Configurations classroom.sdmesa.edu/ssaidane/Docs%20.../ElectronConfiguration.ppt

3 Pauli Exclusion Principle No two electrons in the same atom can have the same set of 4 quantum numbers. That is, each electron in an atom has a unique address of quantum numbers. xbeams.chem.yale.edu/~batista/113/chapter8/ch8.ppt

4 Arrangement of Electrons in Atoms Electrons in atoms are arranged as SHELLS (n) SUBSHELLS (l) ORBITALS (m l ) xbeams.chem.yale.edu/~batista/113/chapter8/ch8.ppt

5 n ---> shell1, 2, 3, 4,... l ---> subshell0, 1, 2,... n - 1 m l ---> orbital -l l m s ---> electron spin+1/2 and -1/2 n ---> shell1, 2, 3, 4,... l ---> subshell0, 1, 2,... n - 1 m l ---> orbital -l l m s ---> electron spin+1/2 and -1/2 4 QUANTUM NUMBERS NUMBERS xbeams.chem.yale.edu/~batista/113/chapter8/ch8.ppt

6 Each orbital can be assigned no more than 2 electrons! This is tied to the existence of a 4th quantum number, the electron spin quantum number, m s. Arrangement of Electrons in Atoms xbeams.chem.yale.edu/~batista/113/chapter8/ch8.ppt

7 Electron Spin Quantum Number, m s Can be proved experimentally that electron has a spin. Two spin directions are given by m s where m s = +1/2 and -1/2. Can be proved experimentally that electron has a spin. Two spin directions are given by m s where m s = +1/2 and -1/2. xbeams.chem.yale.edu/~batista/113/chapter8/ch8.ppt

8 Electrons in Atoms When n = 1, then l = 0 this shell has a single orbital (1s) to which 2e- can be assigned. this shell has a single orbital (1s) to which 2e- can be assigned. When n = 2, then l = 0, 1 2s orbital 2e- 2s orbital 2e- three 2p orbitals6e- three 2p orbitals6e- TOTAL = 8e- xbeams.chem.yale.edu/~batista/113/chapter8/ch8.ppt

9 Electrons in Atoms When n = 3, then l = 0, 1, 2 3s orbital 2e- 3s orbital 2e- three 3p orbitals6e- three 3p orbitals6e- five 3d orbitals10e- TOTAL = 18e- When n = 3, then l = 0, 1, 2 3s orbital 2e- 3s orbital 2e- three 3p orbitals6e- three 3p orbitals6e- five 3d orbitals10e- TOTAL = 18e- xbeams.chem.yale.edu/~batista/113/chapter8/ch8.ppt

10 Electrons in Atoms When n = 4, then l = 0, 1, 2, 3 4s orbital 2e- 4s orbital 2e- three 4p orbitals6e- three 4p orbitals6e- five 4d orbitals10e- seven 4f orbitals14e- seven 4f orbitals14e- TOTAL = 32e- And many more! xbeams.chem.yale.edu/~batista/113/chapter8/ch8.ppt

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12 Filling Diagram for Sublevels Aufbau Principle classroom.sdmesa.edu/ssaidane/Docs%20.../ElectronConfiguration.ppt

13 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 configs. One is called the spdf notation. xbeams.chem.yale.edu/~batista/113/chapter8/ch8.ppt

14 Writing Atomic Electron Configurations Two ways of writing configs. Other is called the 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 xbeams.chem.yale.edu/~batista/113/chapter8/ch8.ppt

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16 The periodic table can be used as a guide for electron configurations. The period number is the value of n. Groups 1A and 2A have the s-orbital filled. Groups 3A - 8A have the p-orbital filled. Groups 3B - 2B have the d-orbital filled. The lanthanides and actinides have the f-orbital filled. Electron Configurations and the Periodic Table classroom.sdmesa.edu/ssaidane/Docs%20.../ElectronConfiguration.ppt

17 Blocks and Sublevels We can use the periodic table to predict which sublevel is being filled by a particular element. classroom.sdmesa.edu/ssaidane/Docs%20.../ElectronConfiguration.ppt

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