Download SIA Chapter 12 Atoms PP

Conceptual
Physical
Science
5th Edition
Chapter 12:
ATOMS AND THE
PERIODIC TABLE
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Do Now
• What are the 6 most important elements
for living things?
• What types of compounds are made of
these elements?
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Movie Clip
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This lecture will help you
understand:
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Atoms Are Ancient and Empty
The Elements
Protons and Neutrons
The Periodic Table
Periods and Groups
Physical and Conceptual Models
Identifying Atoms Using the Spectroscope
The Quantum Hypothesis
Electron Waves
The Shell Model
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Atoms Are Ancient and Empty
Atoms are:
• ancient
—origin of most
atoms goes back
to birth of universe
• mostly empty space
Elements heavier than
hydrogen and much of
the helium were
produced in the interiors
of stars.
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The Elements
• Element: A material made of only one kind
of atom.
– Pure gold is an example as it is made of only
gold atoms.
• Atom: The fundamental unit of an element.
The term “element” is used when referring to macroscopic quantities.
The term “atom” is used when discussing the submicroscopic.
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The Elements
Atoms:
• make up all matter around
us
• to date, 115 distinct kinds
of atoms—
90 found in nature,
remainder synthesized
Element
• any material consisting of
only one type of atom
• Each element can be
designated by its atomic
symbol (C for carbon, Au
for gold)
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Protons and Neutrons
Protons:
• carry a positive charge—
same quantity of charge
as electrons
• are about 1800 times as
massive as an electron
• atoms have the same
number of protons in the
nucleus as electrons
surrounding the nucleus of
an electrically neutral atom
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Protons and Neutrons
Electrons:
• carry a negative
charge—same
quantity of charge as
protons
• repel electrons of
neighboring atoms
• this electrical repulsion
that prevents atomic
closeness
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Protons and Neutrons
Atomic number:
is the number of protons in each
element listed in the periodic
table.
Neutrons:
• accompany protons in the
nucleus
• have about the same mass as
protons but no charge, so are
electrically neutral
**Both protons and neutrons are
nucleons because they are in
the nucleus.
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Isotopes and Atomic Mass
Isotopes:
• refers to atoms of the same element that contain the
same number of protons but different numbers of
neutrons in the nucleus
• identified by mass number, which is the total number
of protons and neutrons in the nucleus
• differ only in mass and not by electric charge;
therefore, isotopes share many characteristics
Total number of neutrons =
mass number – atomic number
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Isotopes and Atomic Mass
Atomic mass:
• total mass of the atom(s) [protons, neutrons,
and electrons]
• listed in periodic table as atomic mass unit
One atomic mass unit is equal to
1.661  10–24 gram or 1.661  10–27 kg
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Isotopes and Atomic Mass
CHECK YOUR NEIGHBOR
The atomic number of an element matches the number of
A.
B.
C.
D.
protons in the nucleus of an atom.
electrons in a neutral atom.
both of the above.
none of the above.
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Isotopes and Atomic Mass
CHECK YOUR ANSWER
The atomic number of an element matches the number of
A.
B.
C.
D.
protons in the nucleus of an atom.
electrons in a neutral atom.
both of the above.
none of the above.
Comment:
When the atomic number doesn’t match the number of electrons,
the atom is an ion.
© 2012 Pearson Education, Inc.
Isotopes and Atomic Mass
CHECK YOUR NEIGHBOR
A nucleus with an atomic number of 44 and a mass number
of 100 must have
A.
B.
C.
D.
44 neutrons.
56 neutrons.
100 neutrons.
none of the above.
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Isotopes and Atomic Mass
CHECK YOUR ANSWER
A nucleus with an atomic number of 44 and a mass number
of 100 must have
A.
B.
C.
D.
44 neutrons.
56 neutrons.
100 neutrons.
none of the above.
Comment:
Be sure to distinguish between neutron and nucleon. Of the
100 nucleons in the nucleus, 56 are neutrons. A neutron is a
nucleon, as is a proton.
© 2012 Pearson Education, Inc.
The Periodic Table
• The Periodic Table is a listing of all the
known elements, with:
– their atomic symbols
– atomic numbers
– atomic masses
• It is NOT something to be memorized.
• Instead, we learn how to READ the Periodic
Table.
• A chemist uses the Periodic Table much like a
writer uses a dictionary. NEITHER need be
memorized!
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The Periodic Table
• The way the table is organized tells us much
about the element’s properties
• Elements are grouped as metals, nonmetals,
and metalloids:
– Metals (on left) – shiny, opaque, good conductors,
malleable, ductile, most are solid at room temperature
– Nonmetals (on right) – transparent, poor conductors,
brittle and shatter when hammered, can be solid,
liquid, or gas
– Metalloids (6 elements between metals and
nonmetals) – have both metallic and nonmetallic
properties – they are weak conductors and are used
as semiconductors in computers
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
The Periodic Table
• The elements are highly organized within
the Periodic Table.
• Each vertical column is called a “group”
– Properties of these elements are very similar
– Example – group 18 elements are the Noble
gasses – don’t combine with other elements
• Each horizontal row is called a “period”
– Properties of these elements gradually
change across the table
– Example – atomic size decreases from left to
right
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The Periodic Table
© 2012 Pearson Education, Inc.
The Periodic Table
© 2012 Pearson Education, Inc.
The Periodic Table
© 2012 Pearson Education, Inc.
The Periodic Table
© 2012 Pearson Education, Inc.
The Periodic Table
CHECK YOUR NEIGHBOR
Which is larger: a lithium atom or a fluorine atom?
Li
F
A. A lithium atom
B. A fluorine atom
C. There is no way to tell without memorizing the periodic table.
© 2012 Pearson Education, Inc.
The Periodic Table
CHECK YOUR ANSWER
Which is larger: a lithium atom or a fluorine atom?
Li
F
A. A lithium atom
B. A fluorine atom
C. There is no way to tell without memorizing the periodic table.
© 2012 Pearson Education, Inc.
The Periodic Table
CHECK YOUR NEIGHBOR
Which is larger: an arsenic atom or a sulfur atom?
S
As
A. An arsenic atom
B. A sulfur atom
C. There is no way to tell without memorizing the periodic table.
© 2012 Pearson Education, Inc.
The Periodic Table
CHECK YOUR ANSWER
Which is larger: an arsenic atom or a sulfur atom?
S
As
A. An arsenic atom
B. A sulfur atom
C. There is no way to tell without memorizing the periodic table.
© 2012 Pearson Education, Inc.
Physical and Conceptual Models
• Physical model
replicates a visible
object at a
convenient scale
• Conceptual model
describes a system –
how multiple parts
interact (weather)
• An atom is best
described by a
conceptual model.
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Identifying Atoms Using the Spectroscope
• We see white light
when all of the visible
frequencies reach our
eye at the same time
• Passing white light
through a prism or
diffraction grating
separates the colors
of light according to
frequency
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© 2012 Pearson Education, Inc.
Identifying Atoms Using the Spectroscope
Spectroscope:
• an instrument that
separates and spreads light
into its component
frequencies
• allows analysis of light
emitted by elements when
they are made to glow—
identifies each element by
its characteristic pattern
• Each element emits a
distinctive glow when
energized and displays a
distinctive spectrum.
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Identifying Atoms Using the Spectroscope
Atomic spectrum
is an element’s
fingerprint—a
pattern of discrete
(distinct)
frequencies of
light.
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Identifying Atoms Using the
Spectroscope
Atomic Excitation
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Identifying Atoms Using the
Spectroscope
Three transitions in an atom. The sum of the energies (and
frequencies) for jumps A and B equals the energy (and
frequency) of jump C.
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Identifying Atoms Using the Spectroscope
CHECK YOUR NEIGHBOR
Each spectral line in an atomic spectrum represents
A.
B.
C.
D.
a specific frequency of light emitted by an element.
one of the many colors of an element.
a pattern characteristic of the element.
all of the above.
© 2012 Pearson Education, Inc.
Identifying Atoms Using the Spectroscope
CHECK YOUR NEIGHBOR
Each spectral line in an atomic spectrum represents
A.
B.
C.
D.
a specific frequency of light emitted by an element.
one of the many colors of an element.
a pattern characteristic of the element.
all of the above.
Explanation:
Many lines make up a pattern that is characteristic of the element,
so choice C doesn’t fly. Interestingly, the line shape of each
spectral line is an image of a thin slit in the spectroscope.
© 2012 Pearson Education, Inc.
Identifying Atoms Using the Spectroscope
CHECK YOUR NEIGHBOR
The hydrogen spectrum consists of many spectral lines.
How can this simple element have so many lines?
A.
B.
C.
D.
One electron can be boosted to many different energy levels.
The electron can move at a variety of speeds.
The electron can vibrate at a variety of frequencies.
Many standing electron waves can fit in the shell of the hydrogen
atom.
© 2012 Pearson Education, Inc.
Identifying Atoms Using the Spectroscope
CHECK YOUR NEIGHBOR
The hydrogen spectrum consists of many spectral lines.
How can this simple element have so many lines?
A.
B.
C.
D.
One electron can be boosted to many different energy levels.
The electron can move at a variety of speeds.
The electron can vibrate at a variety of frequencies.
Many standing electron waves can fit in the shell of the hydrogen
atom.
© 2012 Pearson Education, Inc.
Identifying Atoms Using the Spectroscope
CHECK YOUR NEIGHBOR
When an atom is excited, its
A.
B.
C.
D.
electrons are boosted to higher energy levels.
atoms are charged with light energy.
atoms are made to shake, rattle, and roll.
none of the above.
© 2012 Pearson Education, Inc.
Identifying Atoms Using the Spectroscope
CHECK YOUR ANSWER
When an atom is excited, its
A.
B.
C.
D.
electrons are boosted to higher energy levels.
atoms are charged with light energy.
atoms are made to shake, rattle, and roll.
none of the above.
© 2012 Pearson Education, Inc.
Identifying Atoms Using the Spectroscope
CHECK YOUR NEIGHBOR
The frequencies of light emitted by an atom often add up to
A.
B.
C.
D.
a higher frequency of light emitted by the same atom.
a lower frequency of light emitted by the same atom.
both of the above.
none of the above.
© 2012 Pearson Education, Inc.
Identifying Atoms Using the Spectroscope
CHECK YOUR ANSWER
The frequencies of light emitted by an atom often add up to
A.
B.
C.
D.
a higher frequency of light emitted by the same atom.
a lower frequency of light emitted by the same atom.
both of the above.
none of the above.
Explanation:
This follows from two energy transitions in an atom summing to
equal another energy transition. See the next slide.
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Quantum Hypothesis
• Max Planck, German
physicist, hypothesized—
warm bodies emit radiant
energy in discrete
bundles called quanta.
Energy in each energy
bundle is proportional to
the frequency of
radiation.
• Einstein stated that light
itself is quantized. A
beam of light is not a
continuous stream of
energy but consists of
countless small discrete
quanta of energy, each
quantum called a photon.
© 2012 Pearson Education, Inc.
The Quantum
Hypothesis
The Quantum Hypothesis
Is light a wave, or a stream of particles?
Light can be described by both models—it exhibits
properties of both a wave or a particle, depending
on the experiment.
The amount of energy in a photon is directly
proportional to the frequency of light:
E
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
CHECK YOUR NEIGHBOR
In the relationship E  , the symbol  stands for the
frequency of emitted light, and E stands for the
A.
B.
C.
D.
potential energy of the electron emitting the light.
energy of the photon.
kinetic energy of the photon.
all of the above.
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
CHECK YOUR NEIGHBOR
In the relationship E  , the symbol  stands for the
frequency of emitted light, and E stands for the
A.
B.
C.
D.
potential energy of the electron emitting the light.
energy of the photon.
kinetic energy of the photon.
all of the above.
Explanation:
For those answering choice A, note that the energy of the photon
is equal to the difference in energy levels for the electron emitting
the photon—not its value at one energy level.
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The Quantum Hypothesis
CHECK YOUR NEIGHBOR
Which of these has the greatest energy per photon?
A.
B.
C.
D.
Red light.
Green light.
Blue light.
All have the same.
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
CHECK YOUR ANSWER
Which of these has the greatest energy per photon?
A.
B.
C.
D.
Red light.
Green light.
Blue light.
All have the same.
Explanation:
In accord with E  , the highest frequency light has the greatest
energy per photon.
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
CHECK YOUR NEIGHBOR
Which of these photons has the smallest energy?
A.
B.
C.
D.
Infrared.
Visible.
Ultraviolet.
All have the same.
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
CHECK YOUR ANSWER
Which of these photons has the smallest energy?
A.
B.
C.
D.
Infrared.
Visible.
Ultraviolet.
All have the same.
Explanation:
In accord with E  , the lowest frequency radiation has the
smallest energy per photon.
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
Using the quantum hypothesis:
• Danish physicist Niels Bohr
explained the formation of
atomic spectra as follows:
—The potential energy of an
electron depends on its
distance from the nucleus.
—When an atom absorbs a
photon of light, it absorbs
energy. Then a lowpotential-energy electron is
boosted to become a highpotential-energy electron.
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
Using quantum hypothesis:
• When an electron in any energy level drops closer to
the nucleus, it emits a photon of light.
• Bohr reasoned that there must be a number of distinct
energy levels within the atom. Each energy level has
a principal quantum number n, where n is always an
integer. The lowest level is n = 1 and is closest to the
nucleus.
• Electrons release energy in discrete amounts that
form discrete lines in the atom’s spectrum.
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
CHECK YOUR NEIGHBOR
Which of the following is a quantum number?
A.
B.
C.
D.
0.02
0.2
2
2.5
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
CHECK YOUR ANSWER
Which of the following is a quantum number?
A.
B.
C.
D.
0.02
0.2
2
2.5
Explanation:
Quantum numbers are integers only.
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
Bohr’s model explains why atoms don’t
collapse:
• Electrons can lose only specific amounts of
energy equivalent to transitions between
levels.
• An atom reaches the lowest energy level
called the ground state, where the electron
can’t lose more energy and can’t move closer
to the nucleus.
© 2012 Pearson Education, Inc.
The Quantum Hypothesis
Planetary model of the atom:
• Photons are emitted by atoms as electrons
move from higher-energy outer levels to lowerenergy inner levels.
• The energy of an emitted photon is equal to the
difference in energy between the two levels.
• Because an electron is restricted to discrete
levels, only lights of distinct frequencies are
emitted.
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Electron Wave Model
An electron’s wave nature explains why electrons
in an atom are restricted to particular energy
levels.
Permitted energy levels are a natural consequence
of standing electron waves closing in on
themselves in a synchronized manner.
The orbit for n = 1 consists of a single wavelength,
n = 2 is of two wavelengths, and so on.
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Electron Waves
For a fixed circumference, only an integral number
of standing waves can occur, and likewise in the
paths of electrons about the nucleus.
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Electron Shell Model
Electrons behave as if they are arranged in a
series of concentric shells.
Shell – a region of space around the atomic
nucleus where electrons mat reside.
There are at least 7 shells and each shell can hold
only a limited amount of electrons:
1st shell – 2 electrons
2nd and 3rd shells – 8 electrons each
4th and 5th shells – 18 electrons each
6th and 7th shells – 32 electrons each
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
The Shell Model
Cutaway view of shells in the shell model of the
atom
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The Shell Model
Shell model showing the first three periods of the
periodic table
© 2012 Pearson Education, Inc.