Electron Configuration cont’d MS. MCGRATH CHEMISTRY 11

Aufbau principle States that in going from a hydrogen atom to a larger atom, you add protons to the nucleus and electrons to orbitals You start at the orbitals having the lowest energy level and fill them, in order of increasing energy, until you run out of electrons

Pauli exclusion principle States that an orbital can be empty, have one electron, or at most have two electrons

Hund’s rule States that electrons in the same sublevel will not pair up (occupy the same orbital) until all the orbitals in the sublevel have been at least half filled

Electron configurations The lanthanides are the 14 elements removed from period 6 of the periodic table The actinides are the 14 elements removed from period 7 of the periodic table The above two groups do have unique electron configurations

Electronic configuration - Lanthanides Lanthanum, atomic number 57: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 5d 1 or shorthand notation: [Xe]6s 2 5d 1

Electronic configuration - Lanthanides Erbium, atomic number 68: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 5d 1 4f 11 or shorthand notation: [Xe]6s 2 5d 1 4f 11

Electronic configuration - Lanthanides Hafium, atomic number 72: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 5d 1 4f 14 5d 1 or shorthand notation: [Xe]6s 2 5d 1 4f 14 5d 1

Electronic configuration - Lanthanides Note: We place one electron in 5d then we fill up 4f with fourteen electrons then return to 5d and place the remaining nine electrons

Electron configuration - Actinides Now you try: Radium, atomic number 88 Uranium, atomic number 92 Rutherfordium, atomic number 104

Electron configuration - Actinides Radium, atomic number 88: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 5d 1 4f 14 5d 9 6p 6 7s 2 or shorthand notation: [Rn]7s 2

Electron configuration - Actinides Uranium, atomic number 92: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 5d 1 4f 14 5d 9 6p 6 7s 2 6d 1 5f 3 or shorthand notation: [Rn]7s 2 6d 1 5f 3

Electron configuration - Actinides Rutherfordium, atomic 104: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 5d 1 4f 14 5d 9 6p 6 7s 2 6d 1 5f 14 6d 1 or shorthand notation: [Rn]7s 2 6d 1 5f 14 6d 1

Electron configuration - Actinides Note: We place one electron in 6d then we fill up 5f with fourteen electrons then return to 6d and place the remaining nine electrons

Electron configuration - exceptions Chromium and Copper See video and make notes

Electron configuration for ions Watch video and copy notes

Electron configuration for ions Practice