Section 5.2 Electron Arrangement in Atoms

We’ve looked at it this way

Electron Configurations Follow three rules… 1.The Aufbau principle 2.The Pauli Exclusion Principle 3.Hund’s Rule

The Aufbau Principle Electrons occupy the orbitals of lowest energy first

The Pauli Exclusion Principle No two electrons in an atom can have identical quantum numbers. Orbital Notation

Hund’s Rule When an electron is added to sublevel, always occupy empty orbital and only pair when necessary.

Hund’s Rule or Seats on the Bus

Orbital Notation

Electron Configuration for Group 1 H1s 1 Li1s 2 2s 1 Na 1s 2 2s 2 2p 6 3s 1 K 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Rb1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 Cs 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 1 Fr 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 7s 1

Electron Configuration for Group 18 He1s 2 Ne1s 2 2s 2 2p 6 Ar 1s 2 2s 2 2p 6 3s 2 3p 6 Kr 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 Xe1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 Rn 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6

Noble Gas Configuration He1s 2 Ne[1s 2 ] 2s 2 2p 6 Noble Gas Configuration: Ne [He] 2s 2 2p 6 Na [1s 2 2s 2 2p 6 ] 3s 1 Noble Gas Configuration:Na [Ne] 3s 1

Noble Gas Notation Orbital Notation for U Use noble gas notation:

Exceptions to Remember Orbital Notation for Cr: Orbital Notation for Cu:

Exceptions to Remember 29 Cu 47 Ag 79 Au

Exceptions to Remember 24 Cr 42 Mo

Electron Dot Notation Only the highest energy level electrons are drawn. (s & p)

Electron Dot Notation