Download Section 4.2 The Quantum Model of the Atom

Name: _____________________________________________Date: ________________
Chemistry
Mr. Herman
Exeter SHS
Grade 11
Chapter 4.2 The Quantum Model of the Atom
Lesson Notes Worksheet
Vocabulary
Angular momentum quantum number
Heisenberg uncertainty principle
Magnetic quantum number
Orbital
Principle quantum number
Quantum number
Quantum theory
Spin quantum number
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Objectives:
• Explain how the Heisenberg uncertainty principle and the Schrodinger wave equation led
to the idea of atomic orbitals.
• List the four quantum numbers, and describe their significance.
Electrons Act Like Both Particles and Waves
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Thomson’s experiments demonstrated that electrons act like particles that have mass.
In 1924, Louis de Broglie pointed out that the behavior of electrons according to Bohr’s
model was similar to the behavior of waves.
De Broglie suggested that electrons could be considered waves confined to the space
around a nucleus.
• As waves, electrons could have only certain frequencies which correspond to the
specific energy levels.
The present-day model of the atom takes into account both the particle and wave properties
of electrons.
In this model, electrons are located in orbitals, regions around a nucleus that correspond to
specific energy levels.
• Orbitals are regions where electrons are likely to be found.
• Orbitals are sometimes called electron clouds because they do not have sharp
boundaries. Because electrons can be in other places, the orbital has a fuzzy
boundary like a cloud.
According to the current model of an atom, electrons are found in orbitals.
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Quantum Number
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The present-day model of the atom is also known as the quantum model.
• According to this model, electrons within an energy level are located in orbitals,
regions of high probability for finding a particular electron.
• The model does not explain how the electrons move about the nucleus to create
these regions.
To define the region in which electrons can be found, scientists have assigned four
quantum numbers that specify the properties of the electrons.
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A quantum number is a number that specifies the properties of electrons.
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The principal quantum number, symbolized by n, indicates the main energy level occupied
by the electron.
• Values of n are positive integers, such as 1, 2, 3, and 4.
• As n increases, the electron’s distance from the nucleus and the electron’s energy
increases.
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Quantum Numbers of the First 30 Atomic Orbitals
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