1. Electron Configurations

2. Objectives
Apply Pauli exclusion principle, the aufbau principle, and Hund’s rule to write electron configurations using orbital diagrams and electron configuration notation
Define valence electrons and draw electron-dot structures representing an atom’s valence electrons

3. Electron Configuration
The arrangement of electrons in an atom
Atom wants to be in its most stable state…this is the ground state…its lowest energy state
You will be able to write
Ground state electron configurations
Excited state electron configurations

4. Aufbau principle
States that each electron occupies the lowest energy orbital available.
Fill orbitals from lowest energy to highest energy
P. 135 Some features of the principle
All orbitals related to an energy sublevel are of equal energy
In a multi-electron atom, the energy sublevels within a principle energy level have different energies
In order of increasing energy, the sequence of energy sublevels within a principle energy level is s, p, d, f
Orbitals related to energy sublevels within one principle energy level can overlap orbitals related to energy sublevels within another principle level

5. Pauli Exclusion Principle
States that a maximum of two electrons may occupy a single atomic orbital, but only if the electrons have opposite spins.
We use up and down arrows to represent forward and backward electron spin (like spinning tops in two different directions)

7. Hund’s Rule
States that single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can occupy the same orbitals

11. Orbital Filling Sequence

12. Max # of Electrons in each orbital
P = 6
D = 10
F = 14

13. Writing the Configurations
I shall show you now!!!
Lots of practice now!!!

15. Exceptions to Predicted Configurations
Because atoms want to be as stable as possible, their orbitals have to be either half-filled or fully-filled
Cr family
Cu family

16. Abbreviated Configurations
The lazy-man’s way

17. Valence Electrons
Valence electrons are electrons in the atom’s outermost orbitals – generally, those orbitals associated with the atom’s highest principle energy level
Can be no more than 8 electrons in element’s valence shell
Valence electrons are the electrons responsible for forming chemical bonds

19. Lewis Dot Structure Model of element and its valence electrons
Element symbol surrounded by up to 8 dots
Fill in 1 dot on each side at a time and then pair up the dots

20. Homework 5.3 Assessment P.146 #57-64
Write out electron configurations for Elements with atomic # 1-34