Lesson 11:
Electron Configuration
By: PHILIP R. FELIX
Lesson Objectives: At the end of the lesson, the student will be able to:
1. Define the term electron
configuration.
2. Write the electron configurations for
the elements of the periodic table.
What is Electron Configuration?
The electron configuration
of an atom is the representation
of the arrangement of electrons
distributed among the orbital
shells and subshells.
What is Valence Electron?
A valence electron is an electron in
the outermost shell associated with
an atom, and that can participate
in the formation of a chemical
bond.
Periodic Table Blocks
● Different sections or blocks within
the periodic table correspond to
the s, p, d, and f, sublevels.
● We can “build” the electron
configurations of atoms by reading
the periodic table in order of
increasing atomic number.
The s Block
The s block includes
● Hydrogen and helium
● Elements in Group 1A (1)
● Elements in Group 2A (2)
Elements in the s block have their final
one or two electrons in an s orbital.
The p Block
- The p block consists of
elements in Group 3s (13) to
Group 8A (18).
- There are six p block
elements in each period,
because three p orbitals can
hold up to six electrons.
The d Block
- The d block contains
transition elements. The d
sublevels are one less (n-1)
than the period number.
- There are 10 elements in each
d block, because d orbitals can
hold up to 10 electrons.
The f Block
- The f block contains inner transition elements, two rows at
the bottom of the periodic table. The f sublevels is two less
than the period number.
- There are 14 elements in each f block, because there are
seven f orbitals that can hold up to 14 electrons.
Guide to Writing Electron Configuration
Rules for Electron Configuration
• In order to write electron configuration, we
need to know the RULES.
• 3 rules govern electron configuration.
• Aufbau Principle
• Pauli Exclusion Principle
• Hund’s Rule
• Using the orbital filling diagram at the right
will help you figure out HOW to write them
• Start with 1s orbital. Fill each orbital completely
and then go to the next one, until all of the
elements have been accounted for.
Rules for Assigning Electron Orbitals
A. Pauli Exclusion Principle
- States that no two electrons can
have the same four quantum
numbers. The first three (n, I, and
ml) may be the same, but the fourth
quantum number must be different.
One electron is spin up (ms=+1/2)
and the other would spin down (ms =
-1/2)
Rules for Assigning Electron Orbitals
B. Hund’s Rule
- When assigning electrons in orbitals,
each electron will first fill all the orbitals
with similar energy (also referred to as
degenerate) before pairing with another
electron in a half filled orbital.
Rules for Assigning Electron Orbitals
C. The Aufbau Process
- States that an electron occupies orbitals in order from
lowest energy to highest. The Aufbau (German for building
up, construction) principle is sometimes referred to as the
"building up" principle. It is worth noting that in reality, atoms
are not built by adding protons and electrons one at a time,
and that this method is merely an aid to understand the end
result.
Writing Electron Configurations
1. Orbital Diagram
- This is a visual way to
reconstruct the electron
configuration by showing each
of the separate orbitals and the
spins on the electrons.
Writing Electron Configurations
2. SPDF Notation
- the most common way to describe electron
configurations is to write distributions in the
spdf notation. The total number of electrons
in each energy level is describe by a
superscript that follows the relating energy
level.
Writing Electron Configurations
3. Noble Gas Notation
- the noble gas in the period above the
element that is being analyzed is used to
denote the subshells that the element has
filled and after which the valence electrons
are written.
Thank you
for
Listening!
