The Wave-Mechanical Model
The Wave-Mechanical Model
• The Bohr Model was able to explain the empty space
and the small dense center nature of the atom.
• The Bohr model was also able to explain the unique
emission spectra for each element.
• However, the Bohr Model had some major flaws that
Bohr himself identified.
– If electrons in an atom circle the nucleus (like a planet
circles the sun) it would continuously emit energy and its
orbit would decay eventually causing the electron to crash
into the nucleus and electrons don’t do this!
– Also, Bohr’s model could only accurately describe the
emission spectra for hydrogen in a mathematical fashion.
∆E = -2.17810-18
[
1 - 1
nf2 ni2
]
The Wave-Mechanical Model
• The Bohr Model could ONLY accurately explain the
complete behavior of an atom with only ONE electron
hydrogen.

• In the early 1900’s, it was determined that electrons has
wave properties and in the 1920’s, a new atomic theory,
called the wave-mechanical model, was developed.
• In this model, electrons are conceptualized as waves or
clouds of negative charge that have no specific location
but instead have locations of high and low probability!
• The locations of highest probability are called orbitals!
The Wave-Mechanical Model
• In the wave-mechanical model the atom is still viewed
as having mostly empty space with a small, dense, and
positively charged nucleus.
• The electrons, however, are pictured as diffuse cloud of
negative charge that have no specific location but instead
have locations of high and low probability.
• The locations of highest probability are called orbitals!
hydrogen
A period-3
element
• The wave-mechanical model
is sometimes referred to as the electron-cloud model.
The Wave-Mechanical Model
• DO NOT CONFUSE THE BOHR MODEL WITH THE
WAVE-MECHANICAL MODEL!
Bohr Model
(the planetary model):
Electrons are particles of
matter that circle the
nucleus in orbits (shells)
much as planets circle
(orbit) the sun.
VS
Wave-Mechanical Model
(electron cloud model):
Electrons are waves of
negative charge that are
found in probability locations
called orbitals which are in
found in shells.
e-
hydrogen
hydrogen