Electron Configurations

1
Section 4-3

• Electron Configurations

2
Quantum Mechanical Model

• Energy Levels have sublevels
• Each sublevel contains orbitals
• Orbital a 3-D region around the nucleus that
  indicates the probable location of an electron
• Every orbital can hold 2 electrons

3
Types of Sublevels

• S Sublevel 1 orbital
• Sphere shaped
• Holds 2 electrons
• P Sublevel 3 orbitals
• Dumbbell shaped
• Holds 6 electrons

• D Sublevel 5 orbitals
• Holds 10 electrons
• F sublevel 7 orbitals
• Holds 14 electrons

4
Orbital Shapes
5
Energy Level Sublevels of orbitals electrons/ orbital
1 s 1 2
2 s P 1 3 2 6
3 s P d 1 3 5 2 6 10
4 s p d f 1 3 5 7 2 6 10 14
6
Electron Configurations

• Arrangement of electrons in an atom
• Distinct for each element because they all have
  different numbers of electrons.
• Electrons assume arrangements that have the
  lowest possible energies

7
Aufbau Principle

• Electrons are added one at a time to the lowest
  energy orbital until all the electrons have been
  accounted for.
• Ex the 4s sublevel gets filled before the 3d
  sublevel

8
Pauli Exclusion Principle

• An orbital can hold a maximum of two electrons.
• To occupy the same orbital, the 2 electrons must
  spin in opposite directions.

9
Hunds Rule

• The electrons fill up all the orbitals of the
  sublevel with parallel spins before they begin to
  pair up.

10
Electron Configurations

• Al 1s2 2s2 2p6
• 3s2 3p1
• S 1s2 2s2 2p6
• 3s2 3p4