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Chapter Outline
2.1
2.2
2.3
2.4
2.5
2.6
2.7
The Rutherford Model of Atomic Structure
Nuclides and Their Symbols
Navigating the Periodic Table
The Masses of Atoms, Ions, and Molecules
Moles and Molar Mass
Making Elements
Artificial Nuclides
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Average Atomic Mass
Weighted average mass of natural sample of an element,
calculated by multiplying the natural abundance of each
isotope by its exact mass in amu’s and then summing up
these products.
AM = (mass 1)(abn) + (mass 2)(abn) + (mass 3)(abn) +………
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One Mole of:
C
S
Hg
Cu
Fe
Molecular Mass
Molecular Mass – the sum of the average atomic masses of the atoms in it.
e.g. H2SO4
NOTE: the terms mass and weight are used interchangeably, e.g.
molecular weight (MW) or atomic weight (AW)
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Formula Units and Formula Mass
Formula Units – for ionic compounds,
the smallest electrically neutral unit in
an ionic compound
Formula Mass – the sum of the
average atomic masses of the cations
and anions that make up a neutral
formula unit
e.g. NaCl
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Chapter Outline
2.1
2.2
2.3
2.4
2.5
2.6
2.7
The Rutherford Model of Atomic Structure
Nuclides and Their Symbols
Navigating the Periodic Table
The Masses of Atoms, Ions, and Molecules
Moles and Molar Mass
Making Elements
Artificial Nuclides
© 2014 W. W. Norton Co., Inc.
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The Mole - The mole is the
Chemist’s counting unit
dozen
= 12
pair
=2
ream =
500
gross
= 144
Avogadro’s Number
(NA) = 6.022 X 1023
= 1 mole of atoms,
molecules, ions, etc.
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Experiment –
how many atoms must be added together so
that the mass in grams = mass in amu’s?
Analogy
using
coins:
Mass ratio = 1 : 5 : 25
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Significance of the Mole
Mass in
amu’s
Equivalent to
Mass in
grams/mole
NA of carbon atoms weighs
__________
NA of iron atoms weighs
__________
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Moles, Mass, and Particles
• To convert between number of particles
and an equivalent number of moles.
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Sample Exercise 2.5
The silicon used to make computer chips has to be extremely pure. Fpr
example, it must contain less than 3 x 10-10 moles of phosphorus (a
common impurity in Si) per mole of silicon. What is this level of impurity
expressed in atoms of phosphorus per mole of Si?
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Using the Molar Mass as a Conversion
Factor for Atoms & Molecules
e.g. carbon
12.011grams
mole
1 mole
12.011grams
e.g. H2SO4 sulfuric acid
98.0 grams
mole
1 mole
98.0 grams
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Moles, Mass, and Particles
grams of
atoms or
molecules
moles of
atoms or
molecules
Numbers of
atoms or
molecules
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Practice: Mole Calculations #1
How many moles of K atoms are present in 19.5
g of potassium?
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Practice: Mole Calculations #2
How many moles are present in 58.4 g of chalk
(CaCO3)?
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Practice: Mole Calculations #3
The uranium used in nuclear fuel exists in nature
in several minerals. Calculate how many moles of
uranium are found in 100.0 grams of carnotite,
K2(UO2)2(VO4)2•3H2O.
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