1
Atomic Theory:
The Nuclear Modelof the Atom
Chapter 5
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Section 5.1
Dalton’s Atomic Theory
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Identify the main features of Dalton’s atomic
theory.
Goal 1
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Precursors to John Dalton’s atomic theory
Law of Definite Composition
The percentage by mass of the elementsin a compound is always the same
Law of Conservation of Mass
In a chemical change, mass is converved
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Dalton’s Atomic Theory (1808)
Each element is made up of tiny,individual particles called atoms.
Atoms are indivisible;
they cannot be created or destroyed
All atoms of each element
are identical in every respect.
Atoms of one element are different
from atoms of any other element.
Atoms of one element may combine with atoms of other
elements, usually in the ratio of small, whole numbers,
to form chemical compoundsPresentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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2
Law of Multiple Proportions
When two elements combine to form more than one
compound, the different weights of one element that
combine with the same weight of the other element are in a simple ratio of whole numbers.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Section 5.2
Subatomic Particles
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Identify the three major subatomic particles by
charge and approximate atomic mass, expressed
in atomic mass units.
Goal 2
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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An atom contains smaller partsknown as subatomic particles.
Electron
1– charge, 0.000549 amu
Proton
1+ charge, 1.00728 amu
Neutronno charge, 1.00867 amu
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
Brooks/Cole, a part of the Thomson Corporation.
Section 5.3
The Nuclear Atom
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3
Describe and/or interpret the Rutherford
scattering experiment and the nuclear model of
the atom.
Goal 3
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
Brooks/Cole, a part of the Thomson Corporation.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
Brooks/Cole, a part of the Thomson Corporation.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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The Nuclear Model of the Atom
Every atom contains an extremelysmall, extremely dense nucleus.
All of the positive charge and nearly all of the mass of
an atom are concentrated in the nucleus.
The nucleus is surrounded by a much
larger volume of nearly empty spacethat makes up the rest of the atom.
The space outside the nucleus is very thinly populated by electrons, the total charge of which exactly balances
the positive charge of the nucleus.Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
Brooks/Cole, a part of the Thomson Corporation.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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The diameter of an atom is approximately 100,000
times the diameter of the
nucleus.
If the nucleus was the size of a pea,
there would be a 1 km distance
from it to its nearest neighbor
1 km
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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4
Section 5.4
Isotopes
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Explain what isotopes of an element are and how
they differ from each other.
Goal 4
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
Brooks/Cole, a part of the Thomson Corporation.
For an isotope of any element whose chemical
symbol is known, given one of the following, state
the other two: (a) nuclear symbol, (b) number of
protons and neutrons, (c) atomic number and mass number.
Goal 5
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
Brooks/Cole, a part of the Thomson Corporation.
Identify the features of Dalton’s atomic theory
that are no longer considered valid, and explain
why.
Goal 6
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Every atom of a particular elementhas the same number of protons.
The number of protons in an atom of anelement is the atomic number, Z
Atoms are electrically neutral
Protons have a 1+ charge
Electrons have a 1– charge
The number of electrons in an atom therefore
must be equal to the number of protons
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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All atoms of an element are not identicalSome have more mass than others
Since the number of protons and electrons
in an atom of an element are fixed,there must be variation in the number
of neutrons that causes this difference in mass
Atoms of the same element that have different
masses—different numbers of neutrons—are called isotopes
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5
An isotope is identified by its mass number, A
Mass number = A =
Total number of protons + neutrons
Mass number = # of protons + # of neutrons
A = Z + # of neutrons
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Name of an Isotope
Elemental name–Mass number
Example:
A carbon atom with 6 protons and 6 neutrons
Mass number: 6 + 6 = 12
Name: carbon-12
What is the name of the carbon
isotope with 7 neutrons?
carbon-13
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Symbol of an Isotope
Known as a nuclear symbol
# of protons + # of neutrons
# of protons Sy
mass number
atomic numberSy
A
Z Sy
Example:
What are the nuclear symbols for
carbon-12 and carbon-13?
12
6C
13
6C
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Section 5.5
Atomic Mass
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Define and use the atomic mass unit (amu).
Goal 7
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Given the relative abundances of the natural
isotopes of an element and the atomic mass of
each isotope, calculate the atomic mass of the element.
Goal 8
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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6
Masses of atoms are expressed inatomic mass units, amu
1 amu the mass of one carbon atom1
12
12 amu the mass of one carbon atom
C atom: 6 p+, 6 n, 6 e–
Since the mass of a p+ and a n are about the
same, and since the mass of an e– is about 0,12 amu = mass of (6 + 6) (p+ + n)
12 amu = mass of 12 nuclear subatomic particles
1 amu = mass of 1 nuclear subatomic particle
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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1 amu = 1.66 x 10–24 g
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Mass Spectrum of Neon Atomic Mass(of an element):
The average mass of all atoms of an
element as they occur in nature.
Chlorine has two natural isotopes:
75.78% is chlorine-35 at 34.968852721 amu
24.22% is chlorine-37 at 36.96590262 amu
What is the atomic mass of chlorine?
0.7578 x 34.968852721 amu =
0.2422 x 36.96590262 amu =
26.50 amu
8.953 amu
35.45 amuPresentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
Brooks/Cole, a part of the Thomson Corporation.
Section 5.6
The Periodic Table
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Distinguish between groups and periods in the
periodic table and identify them by number.
Goal 9
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7
Given the atomic number of an element, use a
periodic table to find the symbol and atomic mass
of that element, and identify the period and group in which it is found.
Goal 10
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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When elements are arranged according
to their atomic masses, certain properties
repeat at periodic intervals(Mendeleev and Meyer, 1869)
Periodic Tableof the Elements
A table that arranges the elements in
order of atomic number with elements
with similar properties in the same column
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Mendeleev had blank spaces in his periodic table.
He averaged the properties of the surrounding elements to predict properties of as-yet
undiscovered elements.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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PeriodsHorizontal rows in the periodic table
Numbered 1–7, top to bottom
(numbers usually not printed)
Groups (or Chemical Families)Vertical columns in the periodic table
U.S. numbering: A groups and B groups
IUPAC numbering: 1-18, left to right
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8
Main group elementsElements in the U.S. A-groups
Transition elementsElements in the U.S. B-groups
MetalsElements on the left of the stair-step line
NonmetalsElements on the right of the stair-step line
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Section 5.7
Elemental Symbols and
the Periodic Table
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Given the name or the symbol of an element in
Figure 5.9, write the other.
Goal 11
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007
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aluminum
argon
bariumberyllium
boron
Al
ArBa
Be
B
BrCa
C
ClCr
bromine
calciumcarbon
chlorinechromium
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cobalt
copperfluorine
helium
hydrogen
CoCu
FHe
H
I
FeKr
Pb
Li
iodineiron
krypton
lead
lithium
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9
magnesium
manganesemercury
neon
nickel
Mg
Mn
Hg
Ne
Ni
N
OP
K
Si
nitrogenoxygen
phosphorus
potassium
silicon
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silver
sodiumsulfur
tin
zinc
Ag
Na
S
Sn
Zn
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