Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
43
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER
5
photons of a specific energy value. An element’s atomic emission
spectrum, therefore, is evidence that an atom can emit light of only
certain specific energies. The explanation of this phenomenon
unlocked the secret of the atom’s electron arrangement.
5.2 Quantum Theory and the Atom
The emission spectrum of an atom indicates that the energy it emits
is quantized, meaning that only certain quantities of energy can be
given off. Niels Bohr used the relatively simple emission spectrum
of the hydrogen atom to propose a new atomic model.
The Bohr atomic model Bohr proposed that hydrogen’s single
electron could orbit at only specific distances from the atom’s
nucleus. When the electron is in the orbit nearest the nucleus, it has
the lowest possible energy. When the electron is in the next larger
orbit, it has a higher energy, and so on through the larger allowed
orbits. The electron can occupy only those specific allowed orbits
and thus can have only the energies associated with those orbits.
When an electron is excited by an outside input of energy, it can
absorb only an amount of energy needed to jump to one of the
higher-energy orbits. When it falls back to a lower-energy orbit, the
electron emits an amount (quantum) of energy equal to the difference in energy between the two orbits. Because the emission
spectrum of hydrogen consisted of several different frequencies,
Bohr assumed that the electron could occupy orbits of several different energies, designated by integers called quantum numbers.
Bohr’s model of the atom, sometimes called the planetary
model, was accepted at the time because it explained hydrogen’s
atomic emission spectrum. However, the model was very limited in
that it only worked for hydrogen.
De Broglie’s waves Recall that Einstein explained the photoelectric effect by reasoning that electromagnetic waves could act like
particles. In 1924, Louis de Broglie turned the tables by theorizing
that particles of matter, specifically electrons, could exhibit the properties of waves—frequency and wavelength. De Broglie proposed
that electrons of only a specific frequency could fit into one of the
possible atomic orbits.
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▲
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
43
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER
5
photons of a specific energy value. An element’s atomic emission
spectrum, therefore, is evidence that an atom can emit light of only
certain specific energies. The explanation of this phenomenon
unlocked the secret of the atom’s electron arrangement.
5.2 Quantum Theory and the Atom
The emission spectrum of an atom indicates that the energy it emits
is quantized, meaning that only certain quantities of energy can be
given off. Niels Bohr used the relatively simple emission spectrum
of the hydrogen atom to propose a new atomic model.
The Bohr atomic model Bohr proposed that hydrogen’s single
electron could orbit at only specific distances from the atom’s
nucleus. When the electron is in the orbit nearest the nucleus, it has
the lowest possible energy. When the electron is in the next larger
orbit, it has a higher energy, and so on through the larger allowed
orbits. The electron can occupy only those specific allowed orbits
and thus can have only the energies associated with those orbits.
When an electron is excited by an outside input of energy, it can
absorb only an amount of energy needed to jump to one of the
higher-energy orbits. When it falls back to a lower-energy orbit, the
electron emits an amount (quantum) of energy equal to the difference in energy between the two orbits. Because the emission
spectrum of hydrogen consisted of several different frequencies,
Bohr assumed that the electron could occupy orbits of several different energies, designated by integers called quantum numbers.
Bohr’s model of the atom, sometimes called the planetary
model, was accepted at the time because it explained hydrogen’s
atomic emission spectrum. However, the model was very limited in
that it only worked for hydrogen.
De Broglie’s waves Recall that Einstein explained the photoelectric effect by reasoning that electromagnetic waves could act like
particles. In 1924, Louis de Broglie turned the tables by theorizing
that particles of matter, specifically electrons, could exhibit the properties of waves—frequency and wavelength. De Broglie proposed
that electrons of only a specific frequency could fit into one of the
possible atomic orbits.
▲
▲