Electron Configurations Chapter 5

Aufbau Principle  Aufbau Principle: Electrons occupy the lowest energy orbital available

Aufbau Principle

Pauli Exclusion Principle  Pauli Exclusion Principle: a maximum of two electrons may occupy a single atomic orbital, only if electrons have opposite spins.

Hund’s Rule  Hund’s Rule: single electrons with the same spin must occupy each equal energy orbital before additional electrons can fill said orbitals.

Orbital Notation  Box represents orbital.  Each box is represented by its principle quantum number and sublevel associated with the orbital.  Ex: C

Electron Configuration Notation  Principle energy level, sublevel and superscript representing number of e-  Ex: C  C 1s 2 2s 2 2p 2

Nobel Gas Notation  Uses Nobel gases to abbreviate electron configuration notation.  Ex:  Na  Na 1s 2 2s 2 2p 6 3s 1  Can be abbreviated by using the previous noble gas  Ne 1s 2 2s 2 2p 6  Na [Ne] 3s 1

Valence Electrons  Valence Electrons: electrons in the outermost orbitals  Chemical properties  Main-group elements periodic table  Ex: C

Electron-dot Structure  Consists of atomic symbol, surrounded by dots representing the atom’s valence electrons.  Ex: C

Exceptions  Tendency for half filled orbital.  Cr, Mo, Cu, Ag, Au  4s 1 3d 5, 5s 1 4d 5, 4s 1 3d 10, 5s 1 4d 10, 6s 1 4f 14 5d 10