Chapter 5 Electron Configuration

Electrons in Energy Levels The maximum number of electrons in any energy level is 2n2 Level 2n2 maximum number of electrons 1 2(1)2 2 2 2(2)2 8 3 2(3)2 18 4 2(4)2 32

Aufbau Principle Electrons are “built-up” by filling various energy levels, starting with lower energies, filling orbitals two at a time. They go into the orbitals one with spin +1/2 ( ), the other with spin - 1/2 ( ). An orbital diagram is useful in showing this arrangement.

Writing Electron Configuration s orbital = maximum 2 electrons (1 shell) p orbital = maximum 6 electrons (3 shells) d orbital = maximum 10 electrons (5 shells) f orbital = maximum 14 electrons (7 shells) Electron order determined by the Aufbau diagram (Aufbau = “building up”).

Writing Electron Configuration Aufbau diagram

Writing Electron Configuration Na 11: 1s2 2s2 2p6 3s1 Na 11 :1s22s22p63s1

Writing Electron Configuration Si 14: 1s2 2s2 2p6 3s2 3p2 Si 14: 1s22s22p63s23p2

Writing Electron Configuration Cl 17: 1s2 2s2 2p6 3s2 3p5 Cl 17: 1s22s22p63s23p5

Writing Atomic Orbitals Use the number of electrons to fill in the atomic orbitals for an element: C 6 1s 2s 2p 3s 3p

Writing Atomic Orbitals Use the number of electrons to fill in the atomic orbitals for an element: Na 11 1s 2s 2p 3s 3p

Writing Atomic Orbitals Use the number of electrons to fill in the atomic orbitals for an element: Si 14 1s 2s 2p 3s 3p