Download Electron Configurations

Definition – the arrangement of electrons
in an atom
 Each element has a unique electron
configuration because each element
has a different number of electrons
 Lowest energy arrangement of electrons
for each element is known as the
Ground State configuration

To build up the electron configuration for
any particular atom, first the energy
levels of the orbitals are determined.
 Then the electrons are added to the
orbitals one by one, according to three
basic rules
 Remember each orbital can have at
most 2 electrons


An electron occupies the lowest-energy
orbital that can receive it.
• The energy level of
an orbital is affected
by two things
• Distance from
nucleus
• Complexity of the
orbital
No two electrons in the same atom can
have the same set of four quantum
numbers.
 This means that the electrons must have
opposite spins to occupy the same
orbital

Orbitals of equal energy are each
occupied by one electron before any
orbital is occupied by a second electron
 All electrons in singly occupied orbitals
must have parallel spins

An unoccupied orbital is represented by
a line
 With the orbital’s name written
underneath the line
 Arrows are used to represent the
electrons
 Up arrows are written first, followed by
down arrows

Eliminates the lines and arrows
 Coefficient gives the energy level
 Letter gives the sublevel
 Superscripts give the number of electrons
at that sublevel
 1s2 Helium has 2 electrons at the 1 s
sublevel


s sublevel has 1 orbitals
› total of 2 electrons

p sublevel has 3 orbitals
› total of 6 electrons

d sublevel has 5 orbitals
› total of 10 electrons

f sublevel has 7 orbitals
› total of 14 electrons