WAVE MECHANICAL MODEL
EMISSION OF ENERGY BY ATOMS
THE ENERGY LEVELS AND
ORBITALS OF HYDROGEN
Lecture for 10/18/07

The Bohr Model of the Atom
Niels Bohr constructed the first quantum model for

hydrogen
 e- orbit the nucleus, like the planets orbit the sun
Model only fits hydrogen atoms

Fundamentally wrong – e- do not orbit the nucleus


The Wave Mechanical Model
Mid-1920’s: evident that Bohr was wrong

De Broglie and Schrodinger: e- have similar behavior

to photons (wave-particle duality) – developed the
Wave Mechanical Model
 Possible to find the probability of locating the e- –
unable to pinpoint the exact location
 There is greater probability at the center,
near the nucleus
 Further from the nucleus = less probability
of finding the e-

The Wave Mechanical Model Cont.
Model doesn’t explain exact location of the e- or

how it moves (speed or acceleration)
Heisenberg Uncertainty Principle: cannot determine

the location or speed of an e- without some
uncertainty
 The more you know about its location, the less you can
determine about the speed, and vice versa.

Emission of Energy by Atoms
An atom enters an excited state when it absorbs

energy
Excited state has greater energy than ground state

(lowest possible energy state)
Some of the excess energy is released as visible

light (colors) – particle returns to ground state

Emission of Energy by Atoms Cont.
If a red photon is emitted, you see the color red.

 Red has less energy and a longer wavelength
If a blue photon is emitted, you see the color blue.

 Blue has more energy and a shorter wavelength.

Energy Levels of Hydrogen
Only 4 different types of photons are seen

Discrete energy levels exist – all hydrogen atoms

emit photons with the same discrete wavelengths
 The energy levels of hydrogen
are quantized = only certain
values are allowed
 All atoms have quantized
energy levels

The Hydrogen Orbitals
orbital: the probability map for the e-

 Boundary contains 90% of the total e- probability
principal energy levels: discrete energy

levels; labeled with integers (n = 1 to 4)
 sublevel: the possible shapes of the orbitals
present at that energy level
• # = principal energy level
• letter = shape
s: spherical
p: two-lobed

The Hydrogen Orbitals Cont.
Comparison of the 1s and 2s orbitals, and the s and

p orbitals:
As the principal energy level increases, the average

distance of the e- from the nucleus also increases
Orbitals are potential space for the e- - all orbitals

exist even when no electrons are in them

The Hydrogen Orbitals Cont.
Ground state: e- in the 1s orbital add energy e-

can move to the 2s or one of the 2p orbitals
Principal energy level 3 contains the following sublevels:

3s, 3p, and 3d…
Even further from the nucleus –
more orbitals possible since
there’s more space available
Principal energy level 4 contains the following sublevels:

4s, 4p, 4d, and the 4f orbitals
 There are seven 4f orbitals: