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Chapter
3
The Atom
The Atom
• ____________ (450 B.C.)
proposed that all matter is
made up of tiny, indivisible
particles. (atomos)
3-2
Laws
• Law of Conservation of
Mass: mass is neither
____________ during
ordinary chemical rxns or
___________ changes.
3-3
Laws
• Law of Definite Proportions:
compounds contain the same
____________ in exactly the same
_____________ by mass
regardless of the _______ of the
sample or the __________ of the
compound.
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Laws
• Law of Multiple Proportions: If two or
more ________________ are
composed of the same ____________,
the _______ of the masses of the
second element combined with a certain
_________ of the first element is always
a ratio of ______________________.
3-5
Daltons Atomic Theory
In 1808 ___________, an
English schoolteacher, came up
with an atomic theory to explain
these laws. Many of the
_________ of his theory still
hold true today.
3-6
Dalton’s Atomic Theory
~ Each ____________ is composed of atoms.
~ Atoms of a given element are __________,
and __________ than those of any other
element.
~ A given compound forms by ____________
of two or more different atoms, always in the
same _______________________ of atoms.
~ Atoms are neither ________________ in any
chemical reaction, only _____________.
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The Structure of the Atom
• ______: the smallest
_________ of an element
that ________ the
chemical ________ of that
element.
3-8
The Discovery of the Electron
• ___________ (1897) an
English physicist who
discovered ________ using
his famous ___________
experiment. He determined
the _______________ ratio.
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The Discovery of the Electron
The Discovery of the Electron
• __________ (1909) an American
__________ who determined the
charge of electrons using his
famous _________ experiment.
The mass of an e- is
approximately ________ the
mass of an atom.
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The Discovery of the Electron
The Discovery of the Electron
Based on these discoveries, two inferences
were made:
1. Because atoms are ____________, they
must contain a ________ charge to
_________ the negative electrons.
2. Because e- are so light in mass _________
to atoms, atoms must contain other
_____________ that account for most of its
mass.
3-13
Plum Pudding Atomic Model
Discovery of the Nucleus
1911, Ernest ________
conducted experiments
with _________ materials
that released only
__________ charged
alpha particles….
3-15
Discovery of the Nucleus
Discovery of the Nucleus
• Rutherford concluded atoms have a
________ core with a _______ charge.
Rutherford’s Atomic Model:
Discovery of the Nucleus
• Rutherford’s student, _________, came
up with a way to explain the location of
e- in the atom:
Discovery of the Nucleus
The electron cloud is the current accepted model of the
atom.
The Atom
• Except for H, all ____________ contain
_____________________.
• A proton has a + charge ____________
_____________to the neg. charged e-.
• Atoms contain _______________ of p+
and e-.
• Neutrons are _____________ neutral.
• P+ and no have almost ____________
masses, electrons weigh 1836 times
______.
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The Atom
• ______________: short range p+ to
p+, p+ to no and no to no forces hold the
nuclear particles together.
• ___________________ (Z): the
number of protons in each atom of a
particular element.
☺The atomic number _________ the element!
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Isotopes
• __________: atoms of the same element
that have _______________ due to different
numbers of __________.
• _____________: the total number of
_______ and _________ that make up the
nucleus of an isotope
~ Isotopes are written with the _____________
written after the element name or symbol with
a _______: ex. Uranium-235 or U-235
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Isotopes
Uranium-235 or U-235
Mass number – atomic number = number of ________
235 (protons + neutrons) – 92 protons = 143 neutrons
This info could also be portrayed using a
_____________:
235U
92
Isotopes
~ In nature, __________ are almost always
found as a ___________ of isotopes
~ Isotopes have ________________
chemical properties
~Isotopes with _______ neutrons have a
higher mass and are often described as
“_______”.
3-24
Isotopes
• Nuclide: a general term for a _________
__________ of an element.
Atomic Mass
• Atomic Mass Unit (____): one amu is
exactly _____ of the mass of a ________
atom.
• _______________: the weighted
average of the atomic masses of the
_________________ isotopes of an
element.
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Calculating the Average
Moles
• _____: the amount of a substance that
contains as many _______ as there are
atoms in exactly 12g of ___________.
Moles
• _____________: the number of
particles in exactly one ______ of a
pure substance ~ 6.02214179 x 1023
(we’ll use __________)
Moles
602,000,000,00
0,000,000,000,
000
If you had 6.02 x 1023 pennies and gave away 1
million a day to every person on earth, it
would take you 3000 years to distribute all
your money!!
3-30
Molar Mass
• ____________: the mass of one mole
of a pure substance.
~ the mass of _________ atoms or
__________ is measured in _____.
The mass of a mole of the same
substance is _____________ the same,
with the units _______.
Ex. H20 = H x 2 = 1.01 x 2 =
2.02
+ O x 1 = 16.00 x 1 = +16.00
18.02
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Molar Mass
1) What is the molar mass of BaCl2?
2) What is the molar mass of NaI?
1) Ba = _ x _____ g/mol = _______
Cl = _ x _____ g/mol = ______
_______ g/mol
2) Na = _ x ______ g/mol = ______
I = _ x _______ g/mol = _______
________ g/mol
3-31
Molar Mass
This photograph
shows one mole of
_______ (NaCl
58.44g/mol), ____
(H2O 18.02 g/mol),
and ____(N2 28.02
g/mol).
3-33
Mass/Mole Conversions
When given the number of
_______, you can find the
_______by:
Moles x _g__ = grams
mole
Ex. 5.0 moles of H2O = X g
5.0 moles x 18.02g = 90. g H2O in 5.0
mol
moles
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Mass/Mole Conversions
Moles x _g_ = moles
mol
Now try these problems:
3) 8.32 moles of barium chloride equals
how many grams?
4) 20.1 moles of sulfur dioxide equals
how many grams?
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Mass/Mole Conversions
3) 8.32 moles of barium chloride equals how
many grams?
8.32 moles BaCl2 x _____ g/mol = _____ grams
BaCl2
4) 20.1 moles of sulfur dioxide equals how
many grams?
20.1 moles SO2 x ______ g/mol = _____ g SO2
3-36
Mass/Mole Conversions
Mass/Mole Conversions
When given the amount in _______, you
can calculate the number of ______ by:
g x mol = moles
g
Ex. 11.2 g NaCl = X moles
___ g NaCl x 1.0 mol NaCl = _____ mols NaCl
58.44g
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Mass/Mole Conversions
g x mol = moles
g
Now try these problems:
5) 50.56 g of sodium chloride
equals how many moles?
6) 329.8 g of ammonia equals how
many moles?
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Mass/Mole Conversions
5) 50.56 g of sodium chloride equals how
many moles?
_______ g NaCl x mole = _____ moles NaCl
_____g
6) 329.8 g of ammonia equals how many
moles?
_____ g NH3 x mole = _____ moles NH3
______g
3-40
Particle/Mole Conversions
You can also calculate between
_______ and number of ________:
(1.0 moles = 6.02 x 1023 particles)
To enter this number into your
calculator, punch in 6.02 _____
button (________) 23.
3-41
Particle/Mole Conversions
Ex. 2.59 moles of marble (CaCO3) contains how many
molecules?
_____ mol CaCO3 x 6.02 x 1023 molecules = ___________
1.0 mol CaCO3
molecules
*Particles can be molecules, atoms or formula units
7) How many molecules are in 5.0 moles of carbon dioxide?
5.0 mol CO2 x ________ molecules =
1.0 mole CO2
__________ molecules CO2
3-42
Particle/Mass Conversions
Ex. What is the mass of 3.25 x1023 molecules
of nitrogen?
3.25 x1023 N2 x ______ g = _____g N2
6.02 x 1023
8) How many molecules are 57.36 g of NaCl?
57.36 g NaCl x__________ = __________
____ g
molecules
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The
End!