Chemistry: Matter and Change

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Chapter Menu
Electrons in Atoms
Section 5.1 Light and Quantized Energy Section
5.2 Quantum Theory and the Atom Section 5.3
Electron Configuration
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Section 5-1
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 raysthat
are emitted by radioactive material
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Section 5-1
Section 5.1 Light and Quantized Energy (cont.)
electromagnetic radiation wavelength frequency amp
litude electromagnetic spectrum
quantum Planck's constant photoelectric
effect photon atomic emission spectrum
Light, a form of electromagnetic radiation, has
characteristics of both a wave and a particle.
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Section 5-1
The Atom and Unanswered Questions

• In Rutherford's model, the atoms mass is
  concentrated in the nucleus and electrons move
  around it.

• The model doesnt explain how the electrons were
  arranged around the nucleus.
• The model doesnt explain why negatively charged
  electrons arent pulled into the positively
  charged nucleus.

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Section 5-1
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
  elements chemical behavior is related to the
  arrangement of the electrons in its atoms.

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Section 5-1
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.

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Section 5-1
The Wave Nature of Light (cont.)

• The wavelength (?) is the shortest distance
  between equivalent points on a wave.

• The frequency (?) is the number of waves that
  pass a given point per second.
• The amplitude is the waves height from the
  origin to a crest.

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Section 5-1
The Wave Nature of Light (cont.)
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Section 5-1
The Wave Nature of Light (cont.)

• What relationship do you see between
  ?, v, and c?

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Section 5-1
The Wave Nature of Light (cont.)

• The speed of light (3.00 ? 108 m/s) is the
  product of its wavelength and frequency c ??.

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Section 5-1
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.

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Section 5-1
The Wave Nature of Light (cont.)
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• The Wave Nature of Light (cont.)

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• The Wave Nature of Light (cont.)

• Visible Light

Note the trends Blue light has shorter ?, higher
v, and more energy. Red light has longer ?,
lower v, and less energy. http//www.brainpop.co
m/science/energy/electromagneticspectrum/
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Section 5-1
The Particle Nature of Light

• The wave model of light cannot explain all of
  lights 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.

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Section 5-1
The Particle Nature of Light (cont.)

• The wave theory could also not explain the
  photoelectric effect - electrons are emitted from
  a metals surface when light of a certain
  frequency shines on it (how solar calculators
  work).

• http//phet.colorado.edu/en/simulation/photoelectr
  ic

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Section 5-1
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.
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Section 5-1
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.

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Section 5-1
Atomic Emission Spectra (cont.)
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Section 5-1
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 elements atomic emission spectrum is unique
  they have their own fingerprints!

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Section 5-1
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 C. quanta
D. wave-particle

1. A
2. B
3. C
4. D

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Section 5-1
Section 5.1 Assessment
What is a particle of electromagnetic radiation
with no mass called? A. beta particle B. alpha
particle C. quanta D. photon

1. A
2. B
3. C
4. D

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End of Section 5-1
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Section 5-2
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.
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Section 5-2
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.
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Section 5-2
Bohr's Model of the Atom

• Bohr correctly predicted the frequency lines in
  hydrogens 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.

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Section 5-2
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.

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Section 5-2
Bohr's Model of the Atom (cont.)

• Each orbit was given a number, called the quantum
  number.

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Section 5-2
Bohr's Model of the Atom (cont.)

• Hydrogens 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/img/app/library/obje
  cts/Flash/VLObject-1347-070828110836.swf

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Section 5-2
Bohr's Model of the Atom (cont.)
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Section 5-2
Bohr's Model of the Atom (cont.)
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Section 5-2
Bohr's Model of the Atom (cont.)

• Bohrs model explained the hydrogens spectral
  lines, but failed to explain any other elements
  lines.

• The behavior of electrons is still not fully
  understood, but it is known they do not move
  around the nucleus in circular orbits.

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Section 5-2
The Quantum Mechanical Model of the Atom

• Louis de Broglie (18921987) hypothesized that
  particles, including electrons, could also have
  wavelike behaviors.

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Section 5-2
The Quantum Mechanical Model of the Atom (cont.)

• The figure illustrates that electrons orbit the
  nucleus only in whole-number wavelengths.

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Section 5-2
The Quantum Mechanical Model of the Atom (cont.)

• The de Broglie equation predicts that all moving
  particles have wave characteristics.

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Section 5-2
The Quantum Mechanical Model of the Atom (cont.)

• Heisenberg showed it is impossible to take any
  measurement of an object without disturbing it.

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Section 5-2
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.

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Section 5-2
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).

• Schrödingers equation applied equally well to
  elements other than hydrogen!!!

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Section 5-2
The Quantum Mechanical Model of the Atom (cont.)

• The wave function predicts a three-dimensional
  region around the nucleus called the atomic
  orbital.

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Section 5-2
Hydrogen Atomic Orbitals

• Principal quantum number (n) indicates the
  relative size and energy of atomic orbitals.

• n specifies the atoms major energy levels,
  called the principal energy levels.

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Section 5-2
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).

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Section 5-2
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.

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Hydrogen Atomic Orbitals (cont.)

• Orbital Shapes

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Section 5-2
Hydrogen Atomic Orbitals (cont.)
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Hydrogen Atomic Orbitals (cont.)

• n 1 sublevel 1s
• n 2 sublevels 2s 2p
• n 3 sublevels 3s, 3p, 3d
• n 4 sublevels 4s, 4p, 4d, 4f
• The total number of electrons each level can
• hold is determined by the formula 2n2.

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Section 5-2
Section 5.2 Assessment
Which atomic suborbitals have a dumbbell shape?
A. s B. f C. p D. d

1. A
2. B
3. C
4. D

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Section 5-2
Section 5.2 Assessment
Who proposed that particles could also exhibit
wavelike behaviors? A. Bohr B. Einstein
C. Rutherford D. de Broglie

1. A
2. B
3. C
4. D

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End of Section 5-2
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Section 5-3
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
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Section 5-3
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.
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Section 5-3
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.

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Section 5-3
Ground-State Electron Configuration (cont.)
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Section 5-3
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.

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Ground-State Electron Configuration (cont.)

• Hunds 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.

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Section 5-3
Ground-State Electron Configuration (cont.)
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Section 5-3
Ground-State Electron Configuration (cont.)

• Noble gas notation uses noble gas symbols in
  brackets to shorten inner electron configurations
  of other elements.

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Section 5-3
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.

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Section 5-3
Valence Electrons

• Valence electrons are defined as electrons in the
  atoms outermost orbitalsthose associated with
  the atoms highest principal energy level.
• An elements valence electrons determine the
  chemical properties of the element.

• Electron-dot structure consists of the elements
  symbol representing the nucleus and inner
  electrons, surrounded by dots representing the
  elements valence electrons.

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Section 5-3
Valence Electrons (cont.)
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Section 5-3
Section 5.3 Assessment
In the ground state, which orbital does an atoms
electrons occupy? A. the highest
available B. the lowest available C. the n 0
orbital D. the d suborbital

1. A
2. B
3. C
4. D

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Section 5-3
Section 5.3 Assessment
The outermost electrons of an atom are called
what? A. suborbitals B. orbitals C. ground
state electrons D. valence electrons

1. A
2. B
3. C
4. D

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End of Section 5-3
64
Resources Menu
Chemistry Online Study Guide Chapter
Assessment Standardized Test Practice Image
Bank Concepts in Motion
65
Study Guide 1
Section 5.1 Light and Quantized Energy
Key Concepts

• All waves are defined by their wavelengths,
  frequencies, amplitudes, and speeds. c ??

• 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 h?

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Study Guide 1
Section 5.1 Light and Quantized Energy (cont.)
Key Concepts

• White light produces a continuous spectrum. An
  elements emission spectrum consists of a series
  of lines of individual colors.

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Study Guide 2
Section 5.2 Quantum Theory and the Atom
Key Concepts

• Bohrs atomic model attributes hydrogens
  emission spectrum to electrons dropping from
  higher-energy to lower-energy orbits. ?E E
  higher-energy orbit - E lower-energy orbit E
  photon h?

• The de Broglie equation relates a particles
  wavelength to its mass, its velocity, and
  Plancks constant. ? h / m?
• The quantum mechanical model of the atom assumes
  that electrons have wave properties.
• Electrons occupy three-dimensional regions of
  space called atomic orbitals.

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Study Guide 3
Section 5.3 Electron Configuration
Key Concepts

• The arrangement of electrons in an atom is called
  the atoms electron configuration.

• Electron configurations are defined by the aufbau
  principle, the Pauli exclusion principle, and
  Hunds rule.
• An elements valence electrons determine the
  chemical properties of the element.
• Electron configurations can be represented using
  orbital diagrams, electron configuration
  notation, and electron-dot structures.

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Chapter Assessment 1
The shortest distance from equivalent points on a
continuous wave is the A. frequency
B. wavelength C. amplitude D. crest

1. A
2. B
3. C
4. D

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Chapter Assessment 2
The energy of a wave increases as ____.
A. frequency decreases B. wavelength decreases
C. wavelength increases D. distance increases

1. A
2. B
3. C
4. D

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Chapter Assessment 3
Atoms move in circular orbits in which atomic
model? A. quantum mechanical model
B. Rutherfords model C. Bohrs model
D. plum-pudding model

1. A
2. B
3. C
4. D

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Chapter Assessment 4
It is impossible to know precisely both the
location and velocity of an electron at the same
time because A. the Pauli exclusion principle
B. the dual nature of light C. electrons travel
in waves D. the Heisenberg uncertainty
principle

1. A
2. B
3. C
4. D

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Chapter Assessment 5
How many valence electrons does neon have? A. 0
B. 1 C. 2 D. 3

1. A
2. B
3. C
4. D

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STP 1
Spherical orbitals belong to which sublevel?
A. s B. p C. d D. f

1. A
2. B
3. C
4. D

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STP 2
What is the maximum number of electrons the 1s
orbital can hold? A. 10 B. 2 C. 8 D. 1

1. A
2. B
3. C
4. D

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STP 3
In order for two electrons to occupy the same
orbital, they must A. have opposite charges
B. have opposite spins C. have the same spin
D. have the same spin and charge

1. A
2. B
3. C
4. D

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STP 4
How many valence electrons does boron contain?
A. 1 B. 2 C. 3 D. 5

1. A
2. B
3. C
4. D

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STP 5
What is a quantum? A. another name for an atom
B. the smallest amount of energy that can be
gained or lost by an atom C. the ground state
of an atom D. the excited state of an atom

1. A
2. B
3. C
4. D

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CIM
Figure 5.11 Balmer Series Figure 5.12 Electron
Transitions Table 5.4 Electron Configurations
and Orbital Diagrams for Elements 110 Table 5.6
Electron Configurations and Dot Structures
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