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Honors Chemistry
Chapter 4 The Structure of the Atom
Notes Outline
4.1 Early Ideas about Matter
Objectives
• Compare and contrast the atomic models of Democritus, Aristotle, and Dalton.
• Understand how Dalton's theory explains the conservation of mass.
Main Idea: The ancient __________________ tried to explain __________________,
but the scientific study of the __________________ began with
__________________ in the early 1800's.
The Roots of Atomic Theory
• Many ancient scholars believed matter was composed of such things as
__________________, __________________, __________________, and
__________________.
• Many believed matter could be __________________ __________________ into
smaller and smaller pieces.
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__________________ (460–370 B.C.) was the first person to propose the idea
that matter was not infinitely divisible, but made up of individual particles called
__________________.
__________________ (384–322 B.C.) __________________ with Democritus
because he did not believe empty space could exist.
Aristotle’s views went __________________ for 2,000 years until science
developed methods to __________________ the validity of his ideas.
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__________________ revived the idea of the atom in the early 1800s based on
numerous __________________ __________________.
Dalton’s __________________ __________________ easily explained
conservation of mass in a reaction as the result of the __________________,
__________________, or __________________ of atoms.
Dalton’s atomic theory was a huge step toward the current model of the atom;
however, not all of Dalton’s theory was __________________.
Dalton was __________________ about atoms being __________________ since
they can be divided into several __________________ __________________.
Dalton was also wrong about all atoms of a given element having
__________________ __________________. Atoms of the same element can
have slightly different __________________.
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4.2 Defining the Atom
Objectives
• Define atom.
• Distinguish between the subatomic particles in terms of relative charge and mass.
• Describe the structure of the atom, including the locations of the subatomic
particles.
Main Idea: An __________________ is made of a __________________ containing
__________________ and __________________; __________________ move
around the __________________.
The Atom
• The smallest particle of an element that retains the properties of the element is
called an __________________.
• An instrument called the __________________ __________________
__________________ (STM) allows individual atoms to be _________________.
The Electron
• ____________________________________ accidentally discovered the
cathode ray.
• When an __________________ __________________ is applied, a ray of
__________________ travels from the cathode to the anode, called a
__________________ __________________.
• Cathode rays are a stream of particles carrying a __________________ charge.
• The particles carrying a negative charge are known as __________________.
• This figure shows a typical cathode ray tube.
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__________________ measured the effects of both magnetic and electric fields
on the cathode ray to determine the __________________ -to__________________ ratio of a charged particle, then compared it to known
values.
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The mass of the charged particle was much __________________ than a hydrogen
atom, then the lightest known atom.
Thomson received the __________________ __________________ in 1906 for
identifying the first subatomic particle—the __________________
In the early 1910s, __________________ __________________ used the
__________________ -__________________ apparatus shown below to
determine the __________________ of an electron.
Charges change in discrete amounts—__________________, the charge of one
electron (now equated to a single unit, 1–).
With the electron’s charge and charge-to-mass ratio known, Millikan calculated the
__________________ of a single electron.
Matter is __________________.
J.J. Thomson's __________________ __________________ ______________
of the atom states that the atom is a __________________,
__________________ charged sphere containing electrons.
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The Nucleus
• In 1911, __________________ __________________ studied how
__________________ charged __________________ __________________
interacted with solid matter.
• By aiming the particles at a thin sheet of __________________ _____________,
Rutherford expected the paths of the alpha particles to be only
__________________ altered by a collision with an electron.
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Although most of the alpha particles went __________________ the gold foil, a
few of them __________________ __________________, some at large angles.
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Rutherford concluded that atoms are mostly _____________ _______________.
Almost all of the atom's __________________ __________________ and
almost all of its __________________ is contained in a __________________
region in the __________________ of the atom called the _________________.
Electrons are held within the atom by their __________________ to the
positively charged nucleus.
The __________________ __________________ between the positively
charged nucleus and positive alpha particles caused the __________________.
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Rutherford refined the model to include positively charged particles in the nucleus
called __________________.
____________________________ received the Nobel Prize in 1935 for
discovering the existence of __________________, __________________
particles in the nucleus which accounts for the __________________ of an atom’s
mass.
All atoms are made of three fundamental subatomic particles: the
__________________, the __________________, and the _______________.
Atoms are __________________ shaped.
Atoms are mostly __________________ space, and electrons travel __________
the nucleus held by an attraction to the positively charged nucleus.
Scientists have determined that protons and neutrons are composed of subatomic
particles called __________________.
__________________ __________________ can be explained by considering
only an atom's __________________.
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4.3 How Atoms Differ
Objectives
• Explain the role of atomic number in determining the identity of an atom.
• Define an isotope.
• Explain why atomic masses are not whole numbers.
• Calculate the number of electrons, protons, and neutrons in an atom given its mass
number and atomic number.
Main Idea: The number of __________________ and the __________________
__________________ define the type of atom.
Atomic Number
• Each element contains a __________________ positive charge in their nucleus.
• The number of __________________ in the nucleus of an atom identifies the
element and is known as the element’s ________________ ________________.
• The atomic number is called the __________________.
Example Problem 1 Atomic Number Complete the following table.
Element
Pb
Composition of Several Elements
Atomic Number
Protons
82
8
Electrons
30
Practice Problems ( page 116)
12. How many protons and electrons are in each atom?
a. radon
b. magnesium
13. An atom of an element contains 66 electrons. Which element is it?
14. An atom contains 14 protons. Which element is it?
15. Challenge One atom has 9 electrons and 10 neutrons. Another atom has 9 protons
and 9 neutrons. Do these atoms have the same atomic number?
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Isotopes and Mass Number
• All atoms of a particular element have the __________________ number of
__________________ and __________________ but the number of
__________________ in the nucleus can __________________.
• Atoms with the same number of protons but different numbers of neutrons are
called __________________.
• The __________________ __________________ of each isotope is usually
__________________.
• Isotopes containing more neutrons have a ______________ ________________.
• Isotopes have the same __________________ behavior.
• The __________________ is the sum of the protons and neutrons in the nucleus.
• The mass number is called the __________________.
• The __________________ is written as
where ___ is the mass number, ___ is
the atomic number, and ___ is the element symbol.
Example Problem 2 Use Atomic Number and Mass Number A chemistry laboratory has
analyzed the composition of isotopes of several elements. The composition data is given in
the table below. Determine the number of protons, electrons, and neutrons in the isotope
of neon. Name the isotope and give its symbol.
Element
neon
Isotope Composition Data
Atomic Number
Mass Number
10
22
calcium
20
46
oxygen
8
17
iron
26
57
zinc
30
64
mercury
80
204
Symbol
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Practice Problems ( page 118)
16. Determine the number of protons, electrons, and neutrons for the isotopes.
Isotope
Protons
Neutrons
Electrons
calcium-46
oxygen-17
iron-57
zinc-64
mercury-204
17. Challenge An atom has a mass number of 55. Its number of neutrons is the sum of
its atomic number and five. How many protons, neutrons, and electrons does this
atom have? What is the identity of this atom?
Mass of Atoms
• One __________________________ (amu) is defined as 1/12th the mass of a
__________________ atom.
• One __________________ is nearly, but not exactly, __________________ to
one __________________ and one __________________.
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The __________________ of an element is the __________________
__________________ mass of the __________________ of that element.
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Example Problem 3 Calculate Atomic Mass Given the data in the table, calculate the
atomic mass of unknown element X. Then, identify the unknown element, which is used
medically to treat some mental disorders.
Isotope
6
X
7
X
Isotope Abundance for Element X
Mass (amu)
6.015
7.016
Percent Abundance
7.59%
92.41%
Practice Problems ( page 121)
18. Boron (B) has two naturally occurring isotopes: boron-10 (abundance = 19.8%, mass =
10.013 amu) and boron-11 (abundance = 80.2%, mass = 11.009 amu). Calculate the
atomic mass of boron.
19. Challenge Nitrogen has two naturally occurring isotopes, N-14 and N-15. Its atomic
mass is 14.007. Which isotope is more abundant? Explain.
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4.4 Unstable Nuclei and Radioactive Decay
Objectives
• Explain the relationship between unstable nuclei and radioactive decay.
• Characterize alpha, beta, and gamma radiation in terms of mass and charge.
Main Idea: __________________ atoms emit __________________ to gain stability.
Radioactivity
• __________________ reactions can change one element into another element.
• In the late 1890s, scientists noticed some substances __________________
emitted radiation, a process they called __________________.
• The rays and particles emitted are called __________________.
• A reaction that involves a change in an atom's nucleus is called a
__________________ __________________.
Radioactive Decay
• Unstable nuclei __________________ energy by emitting radiation in a
spontaneous process called __________________ __________________.
• Unstable radioactive elements undergo radioactive decay thus forming
__________________ __________________ elements.
• __________________ __________________ is made up of
__________________ charged particles called __________________ particles.
• Each alpha particle contains __________________ and __________________
and has a __________________.
• The figure shown below is a __________________ __________________
showing the radioactive decay of radium-226 to radon-222.
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The mass is __________________ in nuclear equations.
__________________ __________________ is radiation that has a
__________________ charge and emits __________________ particles.
Each beta particle is an __________________ with a __________________.
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__________________ __________________ are high-energy radiation with
__________________ __________________ and are __________________.
Gamma rays account for __________________ of the energy lost during
radioactive decay.
Atoms that contain __________________ or __________________ neutrons
are __________________ and lose energy through radioactive decay to form a
__________________ nucleus.
Few exist in __________________ —most have already decayed to stable forms.
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Example Problem 4 Radioactive Decay Write the balanced nuclear equation for each of
the following radioactive decays.
Radium-226 undergoes alpha decay.
Lead-214 undergoes beta decay.
Practice Problems
20. Write the balance nuclear equation for the following radioactive decays.
a. Actinium-210 undergoes alpha decay.
b. Iodine-131 undergoes beta decay.
c. Cesium-140 undergoes beta decay.
d. Rhenium-162 undergoes alpha decay.
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