Electron Configurations

1
Electron Configurations

• Objectives
• 3.0 Use the periodic table to identify periodic
  trends, including atomic radii, ionization
  energy, electronegativity, and energy levels.
• 3.1 Utilizing electron configurations, Lewis dot
  structures, and orbital notations to write
  chemical formulas

2
Ground State Electron Configurations

• Electron configuration the arrangement of
  electrons in an atom
• What is ground state?
• Three rules define how electrons are arranged in
  an atoms orbitals
• The aufbau principle
• The Pauli exclusion principle
• Hunds rule

3
The Aufbau Principle

• Each electron occupies the lowest energy orbital
  available, according to the aufbau diagram

4
The Pauli Exclusion Principle

• A maximum of 2 electrons may occupy a single
  atomic orbital, but ONLY if the electrons have
  opposite spins (represented by ? and ?).

5
Hunds Rule

• Single electrons with the same spin must occupy
  each equal-energy orbital before additional
  electrons with opposite spins can occupy the same
  orbitals (i.e., 1 ? in each 3p orbital BEFORE a ?
  can pair up with a ? in an orbital).

6
Orbital Diagrams and Electron Configuration
Notations

• These are just 2 different ways to represent an
  atoms electron configuration.

7
Orbital Diagrams

• Have a box for each of the atoms orbitals.
• Boxes contain either ? (1 electron), or ?? (full
  orbital), or may be empty.
• Each box is labeled with the principal quantum
  number and the sublevel associated with the
  orbital.
• Examples on board

8
Electron Configuration Notation

• Shorthand to designate all electrons and their
  orbitals
• Designates principal energy level and sublevel,
  and includes a superscript to show the number of
  electrons in the orbital.
• Example Carbon 1s22s22p2
• What is the electron diagram for carbon?
• Table 5-3, p.137

9
Electron Configuration Notation (cont.)

• What is the electron configuration notation for
  the following elements?
• Helium
• Neon
• Argon
• Krypton
• Xenon
• Radon
• What do these elements have in common?

10
Electron Configuration Notation (cont.)

• Electron configuration notation can be
  abbreviated by noble-gas notation.
• He 1s2
• Ne 1s22s22p6
• So magnesium can be written
• 1s22s22p63s2 -OR-
• Ne3s2
• How would you write phosphorous?