Chapter 9: Electrons in Atoms and the Periodic Table
Date:____________
Section 3: Electron Configurations - Notes
Objectives:
 Apply the Pauli exclusion principle, the aufbau principle, and Hund's rule to write electron
configurations using orbital diagrams and electron configuration notation.
Electron Configuration:

An electron configuration shows how the ____________________________________________
___________________________ for a particular atom.

The _______________________________ states that each electron occupies the lowest energy
orbital available.

__________________________________ states that single electrons must occupy each equalenergy orbital before additional electrons with can occupy the same energy level orbitals.

o
All electrons in singly occupied orbitals must have the ___________________________.
o
___________________________________
The ___________________________________________________ states that a maximum of
two electrons can occupy a single orbital, but only if the electrons have opposite spins.
o
We symbolize this as two arrows pointing in opposite directions.
Orbital Notation Examples:

Write the orbital notation electron configuration for the following atoms or ions. State how
many unpaired electrons are in each.
o
N
o
Cl
o
Al
o
V
o
Li+
o
O2-
Electron Configuration Notation:
 Electron Configurations Using the Periodic Table:
o Read the periodic table from left to right to determine the electron configuration.

Write the ground state electron configuration for the following:
o
C
o
Fe
o
W
o
S2-
Noble Gas Notation:

Noble gas notation uses noble gas symbols in brackets to shorten inner electron configurations
of other elements.
o
The noble gas must have a lower atomic number than the atom or ion that the electron
configuration is being written for.

o
W
o
Eu
o
As
o
O
The aufbau diagram can be used to write correct ground-state electron configurations for all
elements up to and including ________________________________, atomic number 23.

The electron configurations for certain transition metals, like ____________________________
______________________________, do not follow the aufbau diagram due to increased
stability of half-filled and filled sets of s and d orbitals.

o
Chromium:
o
Copper:
These exceptions occur because a ___________________________ d subshell and a
_________________________________ d subshell are particularly stable

The number of ________________________________________________ in a transition metal
series does not change as you move across a period.
o
The transition series represents the filling of core orbitals and the number of outershell
electrons is mostly constant—either __________________.