Download Defining the Atom Reading

4
Atomic Str
Structure
Planning G
Guide
Introducing the
BIGIDEA:
ELECTRONS AND THE STRUCTURE OF ATOMS
Elements
El
are composed
d off particles
i l called atoms, and every atom contains a nucleus and one or more electrons.
Lessons and Objectives
NSES
Print Resources
For the Student
A-2, B-1, B-2,
B-3, E-2, G-2,
G-3
4.1
4.1.1
4.1.2
Defining the Atom p 102–104
Explain how Democritus and John Dalton
described atoms.
Identify instruments used to observe
individual atoms.
Structure of the Nuclear Atom p 105–109
A-1, A-2, B-1, 4.2
B-4, E-2, G-2, 4.2.1 Identify three types of subatomic particles.
4.2.2 Describe the structure of atoms according
G-3
to the Rutherford atomic model.
A-1, A-2, B-1,
B-2, G-1, G-2
4.3
4.3.1
4.3.2
4.3.3
Assessing the
Distinguishing Among Atoms p 112–119
Explain what makes elements and isotopes
different from each other.
Explain how isotopes of an element differ.
Calculate the atomic mass of an element.
BIGIDEA:
Reading and Study
Workbook Lesson 4.1
Lesson Assessment 4.1
p 104
Teaching Resources, Lesson 4.1
Review
Reading and Study
Workbook Lesson 4.2
Lesson Assessment 4.2
p 109
Quick Lab: Using Inference:
The Black Box, p 109
Teaching Resources, Lesson 4.2
Review
Teacher Demo, p 106:
Observing Cathode Rays
Teacher Demo, p 107: Atomic
Model Timeline
Reading and Study
Workbook Lesson 4.3
Lesson Assessment 4.3
p 119
Small-Scale Lab: The Atomic
Mass of “Candium,”
p 120
Teaching Resources, Lesson 4.3
Review
Class Activity, p 114:
Applications of Isotopes
ELECTRONS AND THE STRUCTURE OF ATOMS
Essential Questions
1
1. What components make up an atom?
2. How are atoms of one element different from
atoms of another element?
100A Chapter 4
For the Teacher
Study Guide p 121
STP p 125
Reading and Study
Workbook Self-Check
and Vocabulary Review
Chapter 4
Materials List
FFor the
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Student
Digital Resources
Editable Worksheets
PearsonChem.com
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Lab 5: Atomic Structure:
Rutherford’s Experiment
Lab Practical 5-1: Modeling
Atomic Structure
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Small-Scale Lab, p 120
• mass balance
• coated candies (3 different brands)
• small plastic cups or containers
4.2 Lesson Overview
Cathode-Ray Tubes
Rutherford’s Experiment
Rutherford’s Gold-Foil
Experiment
For the Teacher
Teacher Demo, p 106
• magnet
• cathode ray tube
4.3 Lesson Overview
Understanding Atomic
Number
Determining the
Composition of an Atom
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4.1 Lesson Overview
Quick Lab, p 109
• box containing a regularly shaped object fixed in place
• loose marble
Elements in the Human
Body
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Exam View Assessment Suite
Classroom Resources Disc
(includes editable worksheets)
• Lesson Reviews
• Practice Problems
• Interpret Graphs
• Vocabulary Review
• Chapter Quizzes and Tests
• Lab Record Sheets
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Additional Digital Resources
MATH
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Chapter 4 Problem Set
Weighted Averages
Online Student Edition
Online Teacher’s Edition
4.2 Virtual Chem Lab 4: Thomson Cathode-Ray
Tube Experiment
Virtual Chem Lab 5: Millikan Oil Drop Experiment
Virtual Chem Lab 6: Atomic Structure: Rutherford’s
Experiment
Atomic Structure 100B
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Students go into a virtual lab tour in which
key experiments in the history of atomic
theory are studied in a simulated laboratory
environment.
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Identify the students who struggle with
math by assigning an online math skills
diagnostic test. These students can then
improve and practice math skills using the
MathXL tutorial system.
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Atomic Structure
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Students can practice key problem-solving
skills in an online problem set.
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Students access guided step-by-step
tutorials for solving various atomic structure
problems.
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CHAPTER 4
What’s Online
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A scanning electron
microscope was
used to produce
this color-enhanced
image of nickel
atoms.
Student watch animations of a selected
figures from the chapter followed by
questions to check for understanding.
Students watch an overview of a key
chapter concept using real-world contexts
and concrete examples and analogies. Each
activity includes an interactive animation
followed by analysis questions.
National Science Education Standards
A-1, A-2, B-1, B-2, B-3, B-4, E-2, G-1, G-2, G-3
100
Focus on ELL
1 CONTENT AND LANGUAGE Dissect the chapter title into two parts. Begin with
the word structure. Give examples of real world objects or situations that have
a structure. Explain that this chapter is about the structure of atoms. As a class
brainstorm the meaning of an atom. Have students identify any other words in the
lesson titles that they do not know. Add these words to the classroom word wall.
BEGINNING
LOW Write the unfamiliar words on the board and say them out loud.
HIGH Write the plural, noun, and adjective forms of the word atom.
INTERMEDIATE
LOW Have students use an English dictionary to find the meaning of the unfamiliar
words and write the definitions in their notebooks.
HIGH Have students write an original sentence using each word.
100
Chapter 4
ADVANCED: LOW/HIGH Have students discuss the meaning or synonyms of the
unfamiliar words with an elbow partner.
ELECTRONS AND THE
STRUCTURE OF ATOMS
Essential Questions:
1. What components make up an
atom?
2. How are atoms of one element
different from atoms of another
element ?
CHEMYSTERY
Artifact or Artifake?
Crystal skulls are shaped like
a human skull and carved
from quartz crystal. Crystal
ginated from
skulls are thought to have originated
pre-Columbian Central American cultures. If
so, then crystal skulls would have been carved
several hundred or even thousands of years
ago. They would probably have been carved
using primitive stone, wooden, and bone tools.
Although crystal skulls are displayed in
museums throughout the world, none of them
were found in an actual archaeological dig.
This unusual circumstance has led to some
debate about the history of the skulls. People
have questioned whether crystal skulls were
ever carved by people from ancient civilizations. Are these sculptures true artifacts that
were carved in the pre-Columbian era, or are
they just fakes?
Connect to the BIGIDEA As you read
about the structure of atoms, think about how
scientists could identify whether a crystal skull
is from an ancient civilization or is just a fake.
NATIONAL SCIENCE EDUCATION STANDARDS
B-1, E-1, G-1
Understanding by Design
Students are building toward an understanding of
the characteristics of individual atoms and the structural
differences between different types of atoms.
PERFORMANCE GOALS At the end of Chapter 4,
students will be able to answer the essential
questions by applying their knowledge of the
structure of the nuclear atom. Students will also
be able to distinguish different types of atoms.
ESSENTIAL QUESTIONS Read the essential questions
aloud. Ask Why do you think it important to
understand the structure of the atom? (The
structure of the atom determines the properties of
matter.) Ask Can you predict ways that one atom
might be different from another atom? Do you
think all atoms of gold, for example, are identical
to one another? (Engage students in a discussion
of reasonable predictions.)
Activate prior knowledge by having
students describe what they know
about elements. Use the photo of the atoms to help
students connect to the concepts they will learn in
this chapter. Explain that a scanning-electron
microscope (SEM) produced the image by moving a
beam of electrons across the surface of a sample of
matter. Ask What information does this picture tell
you about the sample being scanned? (All of the
atoms have a similar appearance.) Ask What can you
infer about the sample from this image? (All of the
nickel atoms look alike.) Engage students in a
discussion of what other details of the photo might
tell them about atoms.
BIGIDEA
Have students read over the
CHEMystery. Connect the
CHEMystery to the Big Idea by having students
consider differences in markings caused by carving
the crystals. Carving the crystals with primitive tools
would leave markings that are rough and uneven.
Ask students to predict what a microscopic
inspection of the crystals would show if more
advanced carving methods had been used. Then
have students consider how this microscopic
inspection could be made. As a hint, have students
look at the photo of atoms on this page. Ask How
do you think this technology is used to investigate
the crystal skull mystery? (Discuss all plausible ideas.)
CHEMYSTERY
Introduce the Chapter
IDENTIFY MISCONCEPTIONS Students may think of atoms as either solid spheres
or composed of smaller particles that are close together. Use the activity to help
students develop a clearer understanding of atomic structure.
Activity You will need several small balls of modeling clay, a piece of foam board, and
about fifteen straight pins with ball heads. Place one clay ball and the foam board
on a table. Cluster about 10 of the pins in the center of the foam board to model
an atomic nucleus. Insert the other pins around the rest of the foam board to model
electrons. Ask Which of these is the best model for an atom? (the pins) Ask What
makes the ball of clay a poor model? (It is solid.)
Gently push the balls of clay close together into a sphere. Explain that each ball of
clay represents a particle in the atom. Have students compare this clay sphere to the
pin model. Ask Which model is a better representation of an atom? (pin model)
Why? (The pin model represents tiny particles with a large amount of space between
them. The clay model has no space between the particles.) Explain that in this chapter,
students will begin their study of atomic structure.
Atomic Structure
101
CHAPTER 4
BIGIDEA
LESSON 4.1
Key Objectives
4.1.1 EXPLAIN how Democritus and John
Dalton described atoms.
4.1.2 IDENTIFY instruments used to observe
individual atoms.
4.1Defining the Atom
CHEMISTRY
CH
Additional Resources
Q: How do you study something that you cannot see? It is sometimes fun to
try to figure out what is inside a present before opening it. You could look at
the shape or weight of the box. Or maybe you would shake the box a little to
find out if anything moved around or made noise inside the box. Similar to
how you might study a giftwrapped present, scientists often study things that
cannot be seen with the naked eye. In this lesson, you will learn how scientists obtained information about the atoms that they couldn’t see.
Reading and Study Workbook, Lesson 4.1
Available Online or on Digital Media:
• Teaching Resources, Lesson 4.1 Review
Key Questions
Engage
&
CHEMISTRY
Y
YOU
OU Ask students to think of
objects that require experimental data in order to
“picture” them, either because they are small or
inaccessible. (Sample answers: objects in deep space
or deep underground )
How did the concept of the atom
change from the time of Democritus to
the time of John Dalton?
What instruments are used to
observe individual atoms?
Vocabulary
tBUPN
t%BMUPOTBUPNJDUIFPSZ
Build Background
Explain that early philosophers and scientists
developed models of the atom to help explain the
nature of matter. Tell students that in the same way
that they might use a globe to learn about Earth,
they can use an atomic model to learn about atoms.
Ask Why do people use models? (to study things
too large, too small, or too complex to easily see or
understand) What models do you use or have you
used? ( Sample answers: subway maps or weather
maps) Tell students they will learn more about
atomic models in Lessons 4.2 and 5.1.
National Science Education Standards
A-2, B-1, B-2, B-3, E-2, G-2, G-3
Y U
YO
&YOU
READING SUPPORT
Build Vocabulary: Word
Origins AtomDPNFTGSPNUIF
(SFFLXPSEatomos,NFBOJOH
iJOEJWJTJCMFw How does the
word origin of atom relate to
Dalton’s atomic theory?
Early Models of the Atom
How did the concept of the atom change from the time of
Democritus to the time of John Dalton?
Using your unaided eyes, you cannot see the tiny fundamental particles that make up matter. Yet, all matter is composed of such particles, which are called atoms. An atom is the smallest particle of an
element that retains its identity in a chemical reaction.
The concept of the atom intrigued a number of early scholars.
Although these philosophers and scientists could not observe individual atoms, they still were able to propose ideas about the structure of atoms.
Democritus’s Atomic Philosophy The Greek philosopher
Democritus (460 b.c.–370 b.c.) was among the first to suggest the
Democritus reasoned that atoms were
existence of atoms.
indivisible and indestructible. Although Democritus’s ideas agreed
with later scientific theory, they did not explain chemical behavior. They also lacked experimental support because Democritus’s
approach was not based on the scientific method.
Dalton’s Atomic Theory The real nature of atoms and the connection between observable changes and events at the atomic level were
not established for more than 2000 years after Democritus’s death.
The modern process of discovery regarding atoms began with John
By
Dalton (1766–1844), an English chemist and schoolteacher.
using experimental methods, Dalton transformed Democritus’s
ideas on atoms into a scientific theory. Dalton studied the ratios in
which elements combine in chemical reactions.
102 $IBQUFSt-FTTPO
Focus on ELL
1 CONTENT AND LANGUAGE Direct students’ attention to the words indivisible
and indestructible on this page. Have students identify the roots of these words.
(divisible and destructible) Have students look up the definitions of all four words
in the dictionary. Then, have students use the differences between the definitions
of indivisible and indestructible and their root words to identify the meaning of the
prefix in-. (in- means “not”) Have students brainstorm other words with this prefix
that also have meanings opposite those of their roots.
2 FRONTLOAD THE LESSON Have students draw a compare/contrast table with one
column labeled Democritus and another labeled Dalton. Tell students they will use
their tables to track the similarities and differences between the two men’s beliefs
about the atom as they work through the lesson.
3 COMPREHENSIBLE INPUT Read aloud the four parts of Dalton’s theory,
102
Chapter 4 • Lesson 1
demonstrating each point with molecular models. Use an iron bar, iron filings, and
a magnet to reinforce the concept that different forms of an element all have the
same properties because they are made of the same atoms.
c
b
Atoms of
element A
Atoms of
element B
d
Mixture of atoms
of elements A
and B
Based on the results of his experiments, Dalton formulated
hypotheses and theories to explain his observations. The result of
his work is known as Dalton’s atomic theory, which includes the
ideas illustrated in Figure 4.1 and listed below.
1. All elements are composed of tiny indivisible particles
called atoms.
2. Atoms of the same element are identical. The atoms of any
one element are different from those of any other element.
Compound made
by chemically
combining atoms of
elements A and B
CHEMISTRY
Figure 4.1
Dalton’s Atomic Theory
According to Dalton’s
atomic theory, an element is
composed of only one kind
of atom, and a compound is
composed of particles that
are chemical combinations
of different kinds of atoms.
Interpret Diagrams How
does a mixture of atoms
of different elements differ
from a compound?
&YYOU
Sizing up the Atom
BUILD VOCABULARY Discuss the meaning of the
term scientific theory. (an explanation of the way the
world works, based on observation)
READING STRATEGY Ask students to think about
these questions as they read this chapter.
• What could you do if someone asked you to
describe something that is too small to see?
• How would you find out what it looked like?
Explain
Q: How was John Dalton able
to study atoms even though he
couldn’t observe them directly?
What evidence did he use to
formulate his atomic theory?
Early Models of the Atoms
3. Atoms of different elements can physically mix together or
can chemically combine in simple whole-number ratios to
form compounds.
4. Chemical reactions occur when atoms are separated from
each other, joined, or rearranged in a different combination. Atoms of one element, however, are never changed into
atoms of another element as a result of a chemical reaction.
Foundations for Reading
Figure 4.2 Drops of Mercury
This petri dish contains drops of liquid
mercury. Every drop, no matter its size, has
the same properties. Even if you could make
a drop the size of one atom, it would still
have the chemical properties of mercury.
What instruments are used to observe
individual atoms?
The liquid mercury in Figure 4.2 illustrates Dalton’s concept of
the atom. Whether the size of the drop of mercury is large or
small, all drops have the same properties because they are all
made of the same kind of atoms.
A coin the size of a penny and composed of pure copper
(Cu) is another example. If you were to grind the copper coin
into a fine dust, each speck in the small pile of shiny red dust
would still have the properties of copper. If by some means
you could continue to make the copper dust particles smaller,
you would eventually come upon a particle of copper that
could no longer be divided and still have the chemical properties of copper. This final particle is an atom.
Atoms are very small. A pure copper coin the size of a
penny contains about 2 ñ 1022 atoms. By comparison, Earth’s
population is only about 7 ñ 109 people. There are about
3 ñ 1012 times as many atoms in the coin as there are people on
Earth. If you could line up 100,000,000 copper atoms side by side,
they would produce a line only 1 cm long!
START A CONVERSATION Explain that John Dalton’s
work, published in 1808, became the basis for the
modern atomic theory. This model represented the
atom as a simple sphere with no internal structure.
Point out how experimental data have been used to
test and refine atomic theory over time.
USE VISUALS Direct students’ attention to
Figure 4.1. Ask How many atoms of A and of B
form one particle in Figure 4.1d? (2 A and 1 B) Do
you think that a mixture, shown in Figure 4.1c,
always leads to compounds, shown in Figure 4.1d?
Why? (No; some atoms may not readily combine.)
&
CHEMISTRY
Y
YO
YOU
U Dalton used experimental
methods to mix elements and observe how they
combined with each other. He studied the ratios by
which elements combine with each other to propose
what is now known as Dalton’s atomic theory.
103
Check for Understanding
BIGIDEA
ELECTRONS AND THE STRUCTURE OF ATOMS Assess students’
understanding of Dalton’s atomic theory. Ask How might Dalton have used his
observations of chemical reactions to develop his atomic theory? (Based on his
understanding of chemical reactions, he would most likely know that elements
are present in compounds in fixed proportions, and so might hypothesize that the
atoms of these elements were also present in fixed proportions. He also might
have hypothesized that because the same elements are present in reactants and
products and no new elements appeared as a result of the reaction that atoms can
be rearranged, separated, or joined but that no atoms are changed into atoms of a
new element.)
ADJUST INSTRUCTION If students are having difficulty understanding Dalton’s
atomic theory, review the four parts of the theory and Figure 4.1.
Answers
READING SUPPORT Dalton’s atomic theory states
that atoms are indivisible particles. “Indivisible” is
the meaning of atomos.
FIGURE 4.1 In a mixture of atoms of different
elements, each element in the mixture retains
its chemical properties. In a compound,
different elements have been combined to
form a new substance with chemical properties
different from its component elements. Atoms
are separated, joined, or rearranged.
Atomic Structure
103
LESSON 4.1
a
Sizing up the Atom
USE VISUALS Point out that the image in Figure 4.3
is greatly magnified. Explain that a nanometer
is 1 109 meters. Ask If the nanocars are about
2 nm across, about how many atoms wide are the
nanocars if the average width of the atoms is
1.0 1010 m? (about 20 atoms wide)
Evaluate
The radii of most atoms fall within the range of 5 ñ 10Ź11 m
to 2 ñ 10Ź10 m. Does seeing individual atoms seem impossible?
Despite their small size, individual atoms are observable with
instruments such as scanning electron microscopes. In scanning
electron microscopes, a beam of electrons is focused on the sample.
Electron microscopes are capable of much higher magnifications than
light microscopes.
With the help of electron microscopes, individual atoms can even
be moved around and arranged in patterns. The ability to move individual atoms holds future promise for the creation of atomic-sized
electronic devices, such as circuits and computer chips. An example of
a device made from individual atoms is the nanocar shown in
Figure 4.3. This atomic-scale, or “nanoscale,” technology could
become essential to future applications in medicine, communications,
solar energy, and space exploration.
Informal Assessment
Have students evaluate and criticize the following
statements according to Dalton’s theory.
• “All atoms are identical.” (False. Dalton said: “All
atoms of a given element are identical.”)
• “Chemical reactions occur when atoms of one
element change into atoms of another element.”
(False. Chemical reactions occur when atoms are
separated, joined, or rearranged. The elemental
identity of atoms does not change during
chemical reactions.)
Then have students complete the 4.1 Lesson Check.
Review Dalton’s model of the atom. Discuss how
a scanning electron microscope might be used to
support or contest Dalton’s theory, referring students
back to the opening photo as needed. (No matter
how small the sample, you can see that that there
are many similar atoms in each sample. You could
also see where atoms are and whether they change
after a chemical reaction.)
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LESSON 4.1
Explain
Figure 4.3 Model of a Nanocar
These nanocars are each made of
a single molecule. Each nanocar is
only about 2 nanometers across.
A light-activated paddle wheel on
the car propels the car so it can
move. The arrow represesents the
direction the nanocar moves.
4.1 Lesso
LessonCheck
1.
Review How did Democritus characterize
atoms?
6. Identify What is the range of the radii of
most atoms in nanometers (nm)?
2.
Explain How did Dalton advance the atomic
philosophy proposed by Democritus?
3.
Identify What instrument can be used to
observe individual atoms?
7. Calculate A sample of copper with a mass of
63.5 g contains 6.02 ñ 1023 atoms. Calculate
the mass of a single copper atom.
BIGIDEA
4. Explain In your own words, explain the main ideas
of Dalton’s atomic theory.
ELECTRONS AND THE STRUCTURE OF ATOMS
8. According to Dalton’s theory, is it possible to
convert atoms of one element into atoms of
another? Explain.
5. Evaluate Explain why the ideas on atoms proposed
by Dalton constitute a theory, while the ideas proposed by Democritus do not.
104 $IBQUFSt-FTTPO
Lesson Check Answers
1.
2.
3.
4.
5.
104
Chapter 4 • Lesson 1
as indivisible and indestructible
by using experimental
methods
a scanning electron microscope
Answers should include the ideas
that all matter is composed of atoms;
atoms of different elements differ;
and chemical change involves a
rearrangement of atoms.
Democritus’s ideas were not based
on experimental results and did not
explain chemical behavior. Dalton’s
ideas were empirically based and
did explain chemical behavior; his
experiments showed that the ratios
in which elements combined were
whole numbers.
6.
7.
8.
5 102 nm to 2 101 nm
1.05 1022 g
BIGIDEA Atoms of one element
are never changed into atoms of
another element as a result of a
chemical reaction.