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Sections 6.3-6.5
The Bohr Model, Wave Model,
and Quantum Model
Draw Bohr Models
Describe the wave behavior of matter
Arrange electrons in an atom
Identify energy levels
Apply Heisenberg’s Uncertainty Principle
Describe the quantum mechanical model
Key Terms
Ground state
Excited states
Matter waves
Wave functions
Probability density
Electron density
Electron shell
Bohr Model of the Atom
• In 1913 Niels Bohr proposed
quantum model for the H atom
• Bohr proposed H atom has only
certain allowable energy states
• Lowest state= ground state
• Gaining energy = excited state
Bohr Model of the Atom
• Electrons move in certain, specific,
circular orbitals
• Smaller orbit = lower energy level
• Assigned the allowable electron orbitals
the principle quantum number, n.
• 1st orbit= lowest energy: n=1
• 2nd orbit= 2nd lowest energy: n=2
Bohr Model of the Atom
• Energy is added to an atomelectron
moves to higher energy level
• Electron in “excited state” drops to a
lower energy orbit emits a photon
E = E
higher-energy orbit
– E
lower-energy orbit=
Bohr Model of the Atom
• Problems with Bohr’s model
– Only explained H
– Did not explain why electrons
should only be allowed certain,
specific energy levels
De Broglie
• 1924
• Electrons, like light also had a
particle-wave dual nature
• Only multiples of half wavelengths are
allowed in circular orbits
1 half-wavelength
2 half-wavelengths
3 half-wavelengths
De Broglie
• Formulated an equation for the
wavelength, mass, and velocity of a
Heisenberg Uncertainty
– Fundamentally impossible to know
precisely both the velocity AND
position of a particle at the same
– Cannot measure an object
without disturbing it
Quantum Mechanical Model
• 1926
• Schrödinger
• Limited electrons to only certain energy levels
– Atomic orbital: 3 dimensional area around the
nucleus that predicts the 90 % PROBABLE
location of an electron
Electron Density
Quantum Mechanical
• Assigns principal quantum numbers
(n) relative to sizes and energies of
• (n) specifies atom’s major energy
levels= principle energy levels
• Lowest level= ground state= n= 1
• H has 7 energy levels, n= 1 to
Quantum Mechanical Model
• Principal energy levels contain energy
• Principal energy level 1 has 1
• Principal energy level 2 has 2
• Principal energy level 3 has 3
Energy Sublevels
• s, p, d, and f
• Labeled according to shapes of
• s = spherical
• p = dumbbell
• d and f = not all have same
s and p orbitals
Three p orbitals
d orbitals
Energy Sublevels
• Each orbital contains 2 electron at most
• Principal energy level 1 has 1 sublevel: 1s orbital
• Principal energy level 2 has 2 sublevels: 2s and 2p
• 2p sublevel has 3 dumbbell-shaped p orbitals (2px,
2py, and 2pz)
• Principal energy level 3 has 3 sublevels: 3s, 3p, and 3d
• d sublevels have 5 orbitals
• Principal energy level 4 has 4 sublevels: 4s, 4p, 4d,
and 4f
• f sublevels have 7 orbitals