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Transcript
Electrons in Atoms
Section 5.1 Light and Quantized
Energy
Section 5.2 Quantum Theory and
the Atom
Section 5.3 Electron Configuration
Click a hyperlink or folder tab to view
the corresponding slides.
Exit
Section 5.1 Light and Quantized Energy
• Compare the wave and particle natures of light.
• Define a quantum of energy, and explain how it is
related to an energy change of matter.
• Contrast continuous electromagnetic spectra and
atomic emission spectra.
radiation: the rays and particles —alpha particles,
beta particles, and gamma rays—that are emitted
by radioactive material
Section 5.1 Light and Quantized Energy (cont.)
electromagnetic radiation
quantum
wavelength
Planck's constant
frequency
photoelectric effect
amplitude
photon
electromagnetic spectrum
atomic emission spectrum
Light, a form of electromagnetic
radiation, has characteristics of both a
wave and a particle.
The Atom and Unanswered Questions
• In Rutherford's model, the atom’s mass is
concentrated in the nucleus and electrons
move around it.
• The model doesn’t explain how the electrons
were arranged around the nucleus.
• The model doesn’t explain why negatively
charged electrons aren’t pulled into the
positively charged nucleus.
The Atom and Unanswered Questions
(cont.)
• In the early 1900s, scientists observed
certain elements emitted visible light when
heated in a flame.
• Analysis of the emitted light revealed that an
element’s chemical behavior is related to
the arrangement of the electrons in its
atoms.
The Wave Nature of Light
• Visible light is a type of electromagnetic
radiation, a form of energy that exhibits
wave-like behavior as it travels through
space.
• All waves can be described by several
characteristics.
The Wave Nature of Light (cont.)
• The wavelength (λ) is the shortest
distance between equivof waves that pass
a given point per secondalent points on a
continuous wave.
• The frequency (ν) is the number.
• The amplitude is the wave’s height from the
origin to a crest.
The Wave Nature of Light (cont.)
The Wave Nature of Light (cont.)
• What relationship do you see between
λ, v, and c?
The Wave Nature of Light (cont.)
• The speed of light (3.00  108 m/s) is the
product of it’s wavelength and frequency
c = λν.
The Wave Nature of Light (cont.)
• Sunlight, or visible light, contains a
continuous range of wavelengths and
frequencies.
• A prism separates sunlight into a continuous
spectrum of colors – pg. 138.
• The electromagnetic spectrum includes all
forms of electromagnetic radiation – pg. 139.
The Wave Nature of Light (cont.)
The Wave Nature of Light (cont.)
The Wave Nature of Light (cont.)
• Visible Light
Note the trends: Blue light has shorter λ, higher v, and more energy.
Red light has longer λ, lower v, and less energy.
http://www.brainpop.com/science/energy/electromagneticspectrum/
The Particle Nature of Light
• The wave model of light cannot explain all
of light’s characteristics.
• Matter can gain or lose energy only in small,
specific amounts called quanta.
• Max Planck defined a quantum as the
minimum amount of energy that can be
gained or lost by an atom.
The Particle Nature of Light (cont.)
• The wave theory could also not explain the
photoelectric effect - electrons are emitted from a
metal’s surface when light of a certain frequency
shines on it (how solar calculators work).
•http://phet.colorado.edu/en/simulation/photoelectric
The Particle Nature of Light (cont.)
• Albert Einstein proposed in 1905 that light
has a dual nature.
• Einstein suggested a beam of light has
wavelike and particlelike properties.
• A photon is a particle of electromagnetic
radiation with no mass that carries a quantum
of energy.
Ephoton = h
Ephoton represents energy, h is Planck's
constant (6.626 x 10-34 J-s), &  represents
frequency.
Atomic Emission Spectra
• Light in a neon sign is produced when
electricity is passed through a tube filled
with neon gas and excites the neon atoms.
• The excited atoms emit light to release
energy.
Atomic Emission Spectra (cont.)
Atomic Emission Spectra (cont.)
• The atomic emission spectrum of an
element is the set of frequencies of the
electromagnetic waves emitted by the
atoms of the element.
• Each element’s atomic emission spectrum is
unique – they have their own fingerprints!
Section 5.1 Assessment
What is the smallest amount of energy
that can be gained or lost by an atom?
A. electromagnetic photon
B. beta particle
D
A
0%
C
D. wave-particle
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. quanta
Section 5.1 Assessment
What is a particle of electromagnetic
radiation with no mass called?
A. beta particle
B. alpha particle
D
A
0%
C
D. photon
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. quanta
Section 5.2 Quantum Theory and the Atom
• Compare the Bohr and quantum mechanical models
of the atom.
• Explain the impact of de Broglie's wave article duality
and the Heisenberg uncertainty principle on the
current view of electrons in atoms.
• Identify the relationships among a hydrogen atom's
energy levels, sublevels, and atomic orbitals.
atom: the smallest particle of an element that retains
all the properties of that element, is composed of
electrons, protons, and neutrons.
Section 5.2 Quantum Theory and the Atom (cont.)
ground state
quantum number
de Broglie equation
Heisenberg uncertainty
principle
quantum mechanical model
of the atom
atomic orbital
principal quantum number
principal energy level
energy sublevel
Wavelike properties of electrons help
relate atomic emission spectra, energy
states of atoms, and atomic orbitals.
Bohr's Model of the Atom
• Bohr correctly predicted the frequency lines
in hydrogen’s atomic emission spectrum.
• The lowest allowable
energy state of an atom is
called its ground state.
• When an atom gains
energy, it is in an excited
state.
Bohr's Model of the Atom (cont.)
• Bohr suggested that an electron moves
around the nucleus only in certain allowed
circular orbits - Planetary Atomic Model.
Bohr's Model of the Atom (cont.)
• Each orbit was given a number, called the
quantum number.
Bohr's Model of the Atom (cont.)
• Hydrogen’s single electron is in the n = 1
orbit in the ground state.
• When energy is added, the electron moves to
the n = 2 orbit.
http://www.visionlearning.com/library/flash
_viewer.php?oid=1347&mid=51
Bohr's Model of the Atom (cont.)
Bohr's Model of the Atom (cont.)
Bohr's Model of the Atom (cont.)
• Bohr’s model explained the hydrogen’s
spectral lines, but failed to explain any
other element’s lines.
• The behavior of electrons is still not fully
understood, but it is known they do not move
around the nucleus in circular orbits.
The Quantum Mechanical Model of the Atom
• Louis de Broglie (1892–1987)
hypothesized that particles, including
electrons, could also have wavelike
behaviors.
The Quantum Mechanical Model of the Atom
(cont.)
• The figure illustrates that electrons orbit the
nucleus only in whole-number
wavelengths.
The Quantum Mechanical Model of the Atom
(cont.)
• The de Broglie equation predicts that all
moving particles have wave characteristics.
 represents wavelengths
h is Planck's constant.
m represents mass of the particle.
 represents frequency.
The Quantum Mechanical Model of the Atom
(cont.)
• Heisenberg showed
it is impossible to
take any
measurement of an
object without
disturbing it.
The Quantum Mechanical Model of the Atom
(cont.)
• The Heisenberg uncertainty principle
states that it is fundamentally impossible to
know precisely both the velocity and
position of a particle at the same time.
• The only quantity that can be known is the
probability for an electron to occupy a
certain region around the nucleus.
The Quantum Mechanical Model of the Atom
(cont.)
• Schrödinger treated electrons as waves in
a model called the quantum mechanical
model of the atom (electron cloud model).
• Schrödinger’s equation applied equally well to
elements other than hydrogen!!!
The Quantum Mechanical Model of the Atom
(cont.)
• The wave function predicts a threedimensional region around the nucleus
called the atomic orbital.
Hydrogen Atomic Orbitals
• Principal quantum number (n) indicates
the relative size and energy of atomic
orbitals.
• n specifies the atom’s major energy levels,
called the principal energy levels.
Hydrogen Atomic Orbitals (cont.)
• Energy sublevels are contained within the
principal energy levels. Sublevels are
designated as s, p, d, and f.
• Note: (g, h, & i are also possible).
Hydrogen Atomic Orbitals (cont.)
• Each energy sublevel relates to orbitals of
different shape.
• An orbital is a pair of electrons and can
hold only 2 electrons.
• s orbitals can hold 2 electrons.
• p orbitals can hold 6 electrons.
• d orbitals can hold 10 electrons.
• f orbitals can hold 14 electrons.
Hydrogen Atomic Orbitals (cont.)
Orbital Shapes
Hydrogen Atomic Orbitals (cont.)
Hydrogen Atomic Orbitals (cont.)
•
•
•
•
n=1
n=2
n=3
n=4
sublevel: 1s
sublevels: 2s & 2p
sublevels: 3s, 3p, & 3d
sublevels: 4s, 4p, 4d, & 4f
The total number of electrons each level can
hold is determined by the formula 2n2.
Section 5.2 Assessment
Which atomic suborbitals have a
“dumbbell” shape?
A. s
B. f
D
A
0%
C
D. d
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. p
Section 5.2 Assessment
Who proposed that particles could also
exhibit wavelike behaviors?
A. Bohr
B. Einstein
D
A
0%
C
D. de Broglie
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. Rutherford
Section 5.3 Electron Configuration
• Apply the Pauli exclusion principle, the aufbau
principle, and Hund's rule to write electron
configurations using orbital diagrams and electron
configuration notation.
• Define valence electrons, and draw electron-dot
structures representing an atom's valence electrons.
electron: a negatively charged, fast-moving particle
with an extremely small mass that is found in all forms
of matter and moves through the empty space
surrounding an atom's nucleus
Section 5.3 Electron Configuration (cont.)
electron configuration
aufbau principle
Pauli exclusion principle
Hund's rule
valence electrons
electron-dot structure
A set of three rules determines the
arrangement in an atom.
Ground-State Electron Configuration
• The arrangement of electrons in the atom
is called the electron configuration.
• The aufbau principle states that each
electron occupies the lowest energy orbital
available.
Ground-State Electron Configuration
(cont.)
Ground-State Electron Configuration
(cont.)
• An orbital diagram can be used to show
how electrons are arranged in energy
levels.
• The Pauli exclusion principle states that
a maximum of two electrons can occupy a
single orbital, but only if the electrons have
opposite spins.
Ground-State Electron Configuration (cont.)
• Hund’s rule states
that single electrons
with the same spin
must occupy each
equal-energy orbital
before additional
electrons with
opposite spins can
occupy the same
energy level orbitals.
Ground-State Electron Configuration
(cont.)
Ground-State Electron Configuration
(cont.)
• Noble gas notation uses noble gas
symbols in brackets to shorten inner
electron configurations of other elements.
Ground-State Electron Configuration
(cont.)
• The electron configurations (for chromium,
copper, and several other elements) reflect
the increased stability of half-filled and
filled sets of s and d orbitals.
Valence Electrons
• Valence electrons are defined as
electrons in the atom’s outermost orbitals—
those associated with the atom’s highest
principal energy level.
• An element’s valence electrons
determine the chemical properties of
the element.
• Electron-dot structure consists of the
element’s symbol representing the nucleus
and inner electrons, surrounded by dots
representing the element’s valence electrons.
Valence Electrons (cont.)
Section 5.3 Assessment
In the ground state, which orbital does an
atom’s electrons occupy?
A. the highest available
B. the lowest available
D
A
0%
C
D. the d suborbital
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. the n = 0 orbital
Section 5.3 Assessment
The outermost electrons of an atom are
called what?
A. suborbitals
B. orbitals
D
A
0%
C
D. valence electrons
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. ground state electrons
Chemistry Online
Study Guide
Chapter Assessment
Standardized Test Practice
Image Bank
Concepts in Motion
Section 5.1 Light and Quantized
Energy
Key Concepts
• All waves are defined by their wavelengths, frequencies,
amplitudes, and speeds.
c = λν
• In a vacuum, all electromagnetic waves travel at the
speed of light.
• All electromagnetic waves have both wave and particle
properties.
• Matter emits and absorbs energy in quanta.
Equantum = hν
Section 5.1 Light and Quantized
Energy (cont.)
Key Concepts
• White light produces a continuous spectrum. An
element’s emission spectrum consists of a
series of lines of individual colors.
Section 5.2 Quantum Theory and
the Atom
Key Concepts
• Bohr’s atomic model attributes hydrogen’s emission
spectrum to electrons dropping from higher-energy to
lower-energy orbits.
∆E = E higher-energy orbit - E lower-energy orbit = E photon = hν
• The de Broglie equation relates a particle’s wavelength
to its mass, its velocity, and Planck’s constant.
λ = h / mν
• The quantum mechanical model of the atom assumes
that electrons have wave properties.
• Electrons occupy three-dimensional regions of
space called atomic orbitals.
Section 5.3 Electron Configuration
Key Concepts
• The arrangement of electrons in an atom is called
the atom’s electron configuration.
• Electron configurations are defined by the aufbau
principle, the Pauli exclusion principle, and Hund’s rule.
• An element’s valence electrons determine the chemical
properties of the element.
• Electron configurations can be represented using
orbital diagrams, electron configuration notation, and
electron-dot structures.
The shortest distance from equivalent
points on a continuous wave is the:
A. frequency
B. wavelength
D
A
0%
C
D. crest
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. amplitude
The energy of a wave increases as ____.
A. frequency decreases
B. wavelength decreases
C. wavelength increases
D
C
A
0%
B
D. distance increases
A. A
B. B
C. C
0%
0%
0%
D. D
Atom’s move in circular orbits in which
atomic model?
A. quantum mechanical model
B. Rutherford’s model
D
A
0%
C
D. plum-pudding model
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. Bohr’s model
It is impossible to know precisely both the
location and velocity of an electron at the
same time because:
A. the Pauli exclusion principle
A
0%
D
D. the Heisenberg uncertainty
principle
C
C. electrons travel in waves
A. A
B. B
C. C
0%
0%
0%
D. D
B
B. the dual nature of light
How many valence electrons does neon
have?
A. 0
B. 1
D
A
0%
C
D. 3
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. 2
Spherical orbitals belong to which
sublevel?
A. s
B. p
D
A
0%
C
D. f
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. d
What is the maximum number of electrons
the 1s orbital can hold?
A. 10
B. 2
D
A
0%
C
D. 1
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. 8
In order for two electrons to occupy the
same orbital, they must:
A. have opposite charges
B. have opposite spins
D
A
0%
C
D. have the same spin and charge
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. have the same spin
How many valence electrons does boron
contain?
A. 1
B. 2
D
A
0%
C
D. 5
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. 3
What is a quantum?
A. another name for an atom
A
0%
D
D. the excited state of an atom
C
C. the ground state of an atom
A. A
B. B
C. C
0%
0%
0%
D. D
B
B. the smallest amount of energy
that can be gained or lost by
an atom
Click on an image to enlarge.
Figure 5.11 Balmer Series
Figure 5.12 Electron Transitions
Table 5.4
Electron Configurations and Orbital
Diagrams for Elements 1–10
Table 5.6
Electron Configurations and
Dot Structures
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