Electron Configurations - NOTES
C-2.1 Illustrate electron configurations by using orbital notation for representative elements.
C-2.2 Summarize atomic properties (including electron configuration, ionization energy, electron affinity, atomic size, and ionic size).
Notes/Q’s
Objective: Students will be able to properly write the orbital notation and electron configuration of a given atom.
Appetizer:
What is the difference between the ground and excited state of an electron in an
atom? ________________________________________________________________
______________________________________________________________________

Aufbau Principle
 Electrons fill the lowest energy
orbitals first.
Electron Filling order
KEY POINT: The electron configuration represents the ground state of the
electrons in an atom.
KEY RULES
 Pauli Exclusion Principle
 Each orbital can hold TWO electrons with opposite spins.
 Orbitals can be represented by boxes or horizontal lines.
Each s sublevel has _1_ orbital and can hold __2___ e-.
Each p sublevel has _3_ orbitals & can hold __6___ e-.
Each d sublevel has _5_ orbitals & can hold __10__ e-.

Hund’s Rule
 Within a sublevel, place one e- per orbital before pairing
them.
 “Empty Bus Seat Rule”
Each f sublevel has _7_ orbitals & can hold __14__e-.
B. Notation – EXAMPLE (Oxygen)
EXAMPLE (Chlorine)
Electron Configurations - NOTES
Notes/Q’s
Short-hand (Noble gas) electron configurations:
-

Locate the noble gas right before the element.
Put that noble gases’s symbol in brackets
(This will represent the configuration to this point.)
Then continue writing the configuration according to
the Aufbau principle.
EXAMPLE (SULFUR)
o Longhand Configuration
Shorthand Configuration
 Core e-: Go up one row and over to the Noble Gas.
 Valence e-: On the next row, fill in the # of e- in each
sublevel.
 Example: (germanium)
D. Electron Configuration exceptions:
Copper: (1 e- moves from 4s to the 3d)
o
Shorthand Configuration
Expect:
Period Patterns



Period #
 energy level (subtract for d & f)
A/B Group #
 total # of valence eColumn within sublevel block
 # of e- in sublevel
Actual:
Chromium: (1 e- moves from 4s to the 3d)
Expect:
Actual:
(These more stable configurations occur in Mo and Ag as well.)
Example:
Write the electron configuration and orbital notation of a
neutral atom of Arsenic (As).