Transcript Holt Blue Chapter 4 PowerPoint Slides

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Resources
Chapter Presentation
Bellringers
Transparencies
Standardized Test Prep
Image and Math Focus Bank
Visual Concepts
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Chapter 4
Atoms
Table of Contents
Section 1 Development of the Atomic Theory
Section 2 The Atom
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Chapter 4
Section 1 Development of the
Atomic Theory
Bellringer
The following is a quote by Democritus (c. 460–
c. 370 BCE). Paraphrase this quote in your own words
in your science journal.
“Color exists by convention, sweet by convention,
bitter by convention; in reality nothing exists but
atoms and the void.”
What do you know about Democritus? And why are
his thoughts important?
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Chapter 4
Section 1 Development of the
Atomic Theory
Objectives
• Describe some of the experiments that led to the
current atomic theory.
• Compare the different models of the atom.
• Explain how the atomic theory has changed as
scientists have discovered new information about the
atom.
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Chapter 4
Section 1 Development of the
Atomic Theory
The Beginning of the Atomic Theory
• Around 440 BCE, a Greek philosopher named
Democritus thought that you would eventually end up
with a particle that could not be cut. He called this
particle an atom.
• From Aristotle to Modern Science Aristotle,
another Greek philosopher, disagreed with
Democritus’s ideas. He believed that you would
never end up with a particle that could not be cut.
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Chapter 4
Section 1 Development of the
Atomic Theory
The Beginning of the Atomic Theory,
continued
• Democritus was right, though: Matter is made of
particles, which we call atoms. An atom is the
smallest particle into which an element can be
divided and still be the same substance.
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Chapter 4
Section 1 Development of the
Atomic Theory
Dalton’s Atomic Theory Based on
Experiments
• John Dalton published his atomic theory in 1803. His
theory stated that all substances are made of atoms.
Atoms are small particles that cannot be created,
divided, or destroyed. Atoms of the same element
are exactly alike, and atoms of different elements are
different. Atoms join with other atoms to make new
substances.
• Not Quite Correct The atomic theory was then
changed to describe the atom more correctly.
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Chapter 4
Section 1 Development of the
Atomic Theory
Thompson’s Discovery of Electrons
• Thompson experimented with a cathode-ray tube like
the one shown on the next slide. He discovered
negatively charged particles that are now known as
electrons.
• Like Plums in Pudding After learning that atoms
contain electrons, Thompson proposed a new model
of the atom. Thompson thought that electrons were
mixed throughout an atom, like plums in a pudding.
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Chapter 4
Section 1 Development of the
Atomic Theory
Thompson’s Cathode-Ray Tube Experiment
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Chapter 4
Section 1 Development of the
Atomic Theory
Rutherford’s Atomic “Shooting Gallery”
• In 1909, Ernest Rutherford aimed a beam of small,
positively charged particles at a thin sheet of gold
foil. The next slide shows his experiment.
• Surprising Results Rutherford expected the
particles to pass right through the gold in a straight
line. To Rutherford’s great surprise, some of the
particles were deflected.
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Chapter 4
Section 1 Development of the
Atomic Theory
Rutherford’s Gold-Foil Experiment
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Chapter 4
Section 1 Development of the
Atomic Theory
Where Are the Electrons?
• Far from the Nucleus
Rutherford proposed that in
the center of the atom is a
tiny, positively charged part
called the nucleus.
• Bohr’s Electron Levels In
1913, Niels Bohr proposed
that electrons move around
the nucleus in certain paths,
or energy levels.
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Chapter 4
Section 1 Development of the
Atomic Theory
Where Are the Electrons?, continued
• The Modern Atomic
Theory According to
the current theory, there
are regions inside the
atom where electrons
are likely to found.
These regions are
called electron clouds.
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Chapter 4
Section 1 Development of the
Atomic Theory
Comparing Models of the Atom
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Chapter 4
Section 2 The Atom
Bellringer
Answer the following question:
An atom is the smallest particle into which an element
can be divided and still be that element. Now that
scientists have learned that an atom is made up of
even smaller particles, is this definition still accurate?
Explain your answer in your science journal.
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Chapter 4
Section 2 The Atom
Objectives
• Describe the size of an atom.
• Name the parts of an atom.
• State how atoms of different elements differ.
• State how isotopes differ.
• Calculate atomic masses.
• Describe the role of electrons in an atom.
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Chapter 4
Section 2 The Atom
How Small Is an Atom?
• Scientists know that aluminum is made of averagesized atoms. An aluminum atom has a diameter of
about 0.00000003 cm.
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Chapter 4
Section 2 The Atom
What Is an Atom Made Of?
• The Nucleus Protons are positively charged
particles in the nucleus. Neutrons are the particles of
the nucleus that have no electrical charge.
• Outside the Nucleus Electrons are the negatively
charged particles in atoms. Electrons are found around
the nucleus within electron clouds. All the structures of
the atom can be seen on the next slide.
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Chapter 4
Section 2 The Atom
Parts of an Atom
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Chapter 4
Section 2 The Atom
What Is an Atom Made Of?
• The Nucleus An atom’s nucleus contains
positively charged particles called protons.
• The SI unit used to express the masses of particles
in atoms is the atomic mass unit (amu). Each
proton has a mass of about 1 amu.
• Neutrons are the particles of the nucleus that have
no electrical charge.
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Chapter 4
Section 2 The Atom
What Is an Atom Made Of?, continued
• Outside the Nucleus Electrons are the negatively
charged particles in atoms. Electrons are found
around the nucleus within electron clouds.
• The charges of protons and electrons are opposite
but equal, so their charges cancel out.
• Because an atom has no overall charge, it is
neutral.
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Chapter 4
Section 2 The Atom
How Do Atoms of Different Elements Differ?
• Starting Simply The
hydrogen atom has one
proton and one electron.
• Now for Some
Neutrons The helium
atom has two protons,
two neutrons, and two
electrons.
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Chapter 4
Section 2 The Atom
How Do Atoms of Different Elements
Differ?, continued
• Building Bigger Atoms For bigger atoms, simply
add protons, neutrons, and electrons.
• Protons and Atomic Number The number of
protons in the nucleus of an atom is the atomic
number of that atom. All atoms of an element have
the same atomic number.
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Chapter 4
Section 2 The Atom
Isotopes
• Isotopes are atoms that have the same number of
protons but have different numbers of neutrons.
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Chapter 4
Section 2 The Atom
Isotopes, continued
• Properties of Isotopes An unstable atom is an
atom with a nucleus that will change over time. This
type of isotope is radioactive.
• Telling Isotopes Apart You can identify each
isotope of an element by its mass number. The mass
number is the sum of the protons and neutrons in an
atom.
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Chapter 4
Section 2 The Atom
Isotopes, continued
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Chapter 4
Section 2 The Atom
Isotopes, continued
• Naming Isotopes To identify a specific isotope of an
element, write the name of the element followed by a
hyphen and the mass number of the isotope.
• Calculating the Mass of an Element The atomic
mass of an element is the weighted average of the
masses of all the naturally occurring isotopes of that
element.
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Chapter 4
Section 2 The Atom
Math Focus
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Chapter 4
Section 2 The Atom
The Important Role of Electrons
• The electrons at the
outer layer of the
atom are important to
the atom’s
interactions with its
environment.
• Energy Levels Each
electron cloud exists
at a certain energy
level.
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Chapter 4
Section 2 The Atom
The Important Role of Electrons, continued
• Ions: Electron-Proton Imbalance Valence
electrons are at the outer edge of the atom, so they
are the ones most likely to be lost if the atom loses
electrons.
• The outermost energy level is also where the atom
is most likely to gain electrons.
• Ions are formed when an atom loses or gains
electrons, leaving an unequal number of protons
and electrons.
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Chapter 4
Atoms
Concept Mapping
Use the terms below to complete the concept map
on the next slide.
nucleus
mass number
isotopes
protons
atoms
electrons
atomic number
neutrons
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Chapter 4
Atoms
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Chapter 4
Atoms
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End of Chapter 4 Show
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Chapter 4
Standardized Test Preparation
FCAT
For the following questions, write your answers on a
separate sheet of paper.
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Chapter 4
Standardized Test Preparation
1. British chemist and schoolteacher John Dalton
published a theory that defined atoms in 1803.
Included in his theory was the idea that atoms are
small particles which cannot be divided. One of
the first major challenges to this theory came
nearly 100 years later. Another British scientist,
J.J. Thomson, created an experiment using a
cathode-ray tube and discovered the existence of
negatively charged subatomic particles. What
was the effect of this new information?
Continued on next slide
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Question 1, continued
A. Dalton’s theory was not changed and is still
believed to be true.
B. Dalton’s theory had to be modified in response to
the new information.
C. Two different theories of atoms were developed
and used by different scientists.
D. Thomson’s experiment was changed so that its
results matched Dalton’s theory.
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Question 1, continued
A. Dalton’s theory was not changed and is still
believed to be true.
B. Dalton’s theory had to be modified in response to
the new information.
C. Two different theories of atoms were developed
and used by different scientists.
D. Thomson’s experiment was changed so that its
results matched Dalton’s theory.
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2. The illustration below shows a model of an isotope
of boron. What is the mass of the isotope shown?
F. 5
G. 10
H. 11
I. 16
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2. The illustration below shows a model of an isotope
of boron. What is the mass of the isotope shown?
F. 5
G. 10
H. 11
I. 16
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3. What is the difference between an isotope and an
ion?
A.
An isotope is an atom that has a different number of electrons than
other atoms of the same element have. An ion is a particle that has
an equal number of protons and neutrons.
B.
An isotope is an atom that has a different number of protons than
other atoms of the same element have. An ion is a particle that has
an equal number of protons and electrons.
C.
An isotope is an atom that has a different number of neutrons than
other atoms of the same element have. An ion is a particle that has
an unequal number of protons and electrons.
D.
An isotope is an atom that has a different number of protons than
other atoms of the same element have. An ion is a particle that has
an unequal number of protons and electrons.
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3. What is the difference between an isotope and an
ion?
A.
An isotope is an atom that has a different number of electrons than
other atoms of the same element have. An ion is a particle that has
an equal number of protons and neutrons.
B.
An isotope is an atom that has a different number of protons than
other atoms of the same element have. An ion is a particle that has
an equal number of protons and electrons.
C.
An isotope is an atom that has a different number of neutrons than
other atoms of the same element have. An ion is a particle that has
an unequal number of protons and electrons.
D.
An isotope is an atom that has a different number of protons than
other atoms of the same element have. An ion is a particle that has
an unequal number of protons and electrons.
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4. British scientist Ernest Rutherford proposed a new
model of the atom in 1911. The diagram below
shows his model of the atom.
Continued on next slide
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Question 4, continued
4. What did this model add to atomic theory?
F.
the idea that an atom has a dense, negatively charged
nucleus with electrons surrounding the nucleus at a
distance
G. the idea that an atom has a dense, positively charged
nucleus with electrons surrounding the nucleus at a
distance
H. the idea that an atom has a dense, neutrally charged
nucleus with electrons surrounding the nucleus in an
electron cloud
I.
the idea that an atom has a dense, positively charged
nucleus with electrons surrounding the nucleus in an
electron cloud
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Question 4, continued
4. What did this model add to atomic theory?
F.
the idea that an atom has a dense, negatively charged
nucleus with electrons surrounding the nucleus at a
distance
G. the idea that an atom has a dense, positively charged
nucleus with electrons surrounding the nucleus at a
distance
H. the idea that an atom has a dense, neutrally charged
nucleus with electrons surrounding the nucleus in an
electron cloud
I.
the idea that an atom has a dense, positively charged
nucleus with electrons surrounding the nucleus in an
electron cloud
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5. Which one of the following is true of a neutron?
A. A neutron has half the mass of a proton.
B. A neutron has the same mass as an electron.
C. A neutron is a little more massive than a proton.
D. A neutron is a little more massive than an
electron.
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5. Which one of the following is true of a neutron?
A. A neutron has half the mass of a proton.
B. A neutron has the same mass as an electron.
C. A neutron is a little more massive than a proton.
D. A neutron is a little more massive than an
electron.
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6. Austrian physicist Erwin Schrödinger and German
physicist Werner Heisenberg expanded atomic
theory in the 20th century. They accepted some of
the work of earlier scientists, but they added to
atomic theory with new ideas about electrons.
They did not agree with Neils Bohr’s model that
had electrons moving in definite paths around the
nucleus of an atom. Schrödinger and Heisenberg
concluded that one cannot know exactly where
electrons are in an atom. One can only predict
where electrons are likely to be found.
Continued on next slide
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Question 6, continued
6. What was one of the main contributions of
Schrödinger and Heisenberg to atomic theory?
Current theory identifies regions where electrons
are likely to be found. What are these regions
called?
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Question 6, continued
6. What was one of the main contributions of
Schrödinger and Heisenberg to atomic theory?
Current theory identifies regions where electrons
are likely to be found. What are these regions
called?
Full credit answers should include the following points: One
of the main contributions of Schrödinger and Heisenberg
was the idea that electrons do not travel in definite paths
around the nucleus. Electron clouds are the regions where
electrons are likely to be found, according to current atomic
theory.
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Chapter 4
Section 1 Development of the
Atomic Theory
Thompson’s Cathode-Ray Tube Experiment
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Chapter 4
Section 1 Development of the
Atomic Theory
Rutherford’s Gold-Foil Experiment
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Chapter 4
Section 1 Development of the
Atomic Theory
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Chapter 4
Section 1 Development of the
Atomic Theory
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Chapter 4
Section 2 The Atom
Parts of an Atom
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Chapter 4
Section 2 The Atom
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Chapter 4
Section 2 The Atom
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Section 2 The Atom
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Section 2 The Atom
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Chapter 4
Standardized Test Preparation
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Chapter 4
Section 2 The Atom
Math Focus
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