1. Electron Arrangement
Methods of predicting the arrangement and location of electrons in atoms

2. A. Lewis Dot Structures
valence electrons – e– in an atom’s outermost orbitals (in highest energy level) available for bonding; determine the chemical properties of an element
electron-dot structure – consists of element’s symbol surrounded by dots that represent the atom’s valence e–

3. B. Electron Congifurations p 1 2 3 4 5 6 7
d (n-1)
f (n-2) 6 7
© 1998 by Harcourt Brace & Company

4. S 16e- 1s2 2s2 2p6 3s2 3p4 C. Notations Core Electrons
Longhand Configuration
S 16e-
1s2
2s2
2p6
3s2
3p4
Core Electrons
Valence Electrons
C. Johannesson

5. S 16e- [Ne] 3s2 3p4 Shorthand Configuration
Go up one row and over to the Noble Gas.
Fill in the remaining e- in each sublevel like normal.
S 16e- [Ne] 3s2 3p4

6. Example - Germanium
[Ar]
4s2
3d10
4p2

7. White Board Examples Helium (He) Fluorine (F) Nitrogen (N)
Aluminum (Al)
Sulfur (S)

8. Homework
Do the Lewis dot structure and long and short hand electron configuration for the following elements:
Magnesium (Mg)
Silver (Ag)
Gold (Au)
Bromine (Br)
Europium (Eu)

9. D. Orbital Diagrams Ex: Oxygen
This configuration gives more detail as to where the electrons are located.
orbital – region of high probability of finding e–; maximum of 2 e– per orbital
s sublevel = 1 orbital (2 e–)
p sublevel = 3 orbitals (6 e–)
d sublevel = 5 orbitals (10 e–)
f sublevel = 7 orbitals (14 e–)

10. E. General Rules Pauli Exclusion Principle
Each orbital can hold TWO electrons with opposite spins.

11. E. General Rules Hund’s Rule
Within a sublevel, place one e- per orbital before pairing them.

12. E. General Rules Aufbau Principle
Electrons fill the lowest energy orbitals first.

13. White Board Examples Indium (In) Selenium (Se) Sulfur (S)
Aluminum (Al)

14. Homework Do the orbital diagram for the following elements:
Magnesium (Mg)
Bromine (Br)
Phosphorus (P)
Neon (Ne)