Electron Configuration
Quantum Number

Number that specifies the properties of the
atomic orbitals
 Tells us the distance from the nucleus and
the shape of the orbital
Principal Quantum Number

Main level or shell
 These are the Bohr energy levels
n = 1, n = 2, n = 3
 As n increases, the distance from the
nucleus increases
Sublevel

Each main level is divided into sublevels
 Four types of sublevels
s
p
d
f
S orbitals

Spherical
P orbitals

Dumbell shaped
 One dumbell in each axis
P Orbitals
D orbitals
F orbitals
Orbital

Each sublevel is made of orbitals
 Every orbital can hold 2 electrons




s – 1 orbital – 2 electrons
p – 3 orbitals – 6 electrons
d – 5 orbitals – 10 electrons
f – 7 orbitals – 14 electrons
Main
Level
Sublevel
#
orbitals
# e in
sublevel
Total e
Electron Configuration

Arrangement of electrons in an atom
 Aufbau Principle – electrons fill into an
atom starting with the lowest energy levels
Electron Configuration Polka

F:\Documents\electron configuration.avi
Electron Spin

Way which the electrons rotate on their axis
 Pauli Exclusion Principle – in order for two
electrons to occupy the same orbital, they
must have opposite spin
 Write configuration for
C
S
Higher Order

There are exceptions to the order of filling
as you move to higher levels
Br
Valence Electrons

Electrons in the last main energy level
 These are the electrons involved in
chemical reactions
 There are a maximum of 8 valence electrons
How to find valence e
Write configuration and count electrons in
last main energy level
 Examples: Find valence electrons for
C
Fe
Cl
Draw Dot Structure
C
Fe
Cl
Periodic Table
Demitri Mendeleev

First to publish a chart of the elements
 Arranged by increasing atomic mass with
similar elements in columns
Moseley’s Table

He suggested that the elements are arranged
by atomic number rather than atomic mass
 Periodic Law – chemical and physical
properties are periodic functions of their
atomic numbers
Table Properties

Horizontal Rows are called Periods
 Vertical Columns are called Groups or
Families
 For every group or family, the electron
arrangement is the same
Configuration from the Table

Group tells end configuration, period tells
tells the highest energy level
 Ca in group 2 period 4 so it ends in 4s2
Blocks

Chart is broken into blocks based on the
orbitals they fill last
 Groups 1 and 2 fill s last – called s block
 Groups 3 –12 called d block
 Groups 13 – 18 called p block
 Bottom two rows are the f block
Name the element with the
following end configuration
5s1
 2s22p3
 4s23d6
 3s23p6
 6s25d9

http://modelscience.com/PeriodicTable.html