Modern Chemistry
Chapter 3
Atoms:
the building block of matter
1
Chapter Vocabulary
Law of conservation
of mass
Law of definite
proportions
Law of multiple
proportions
Atom
Nuclear forces
Atomic number
Isotope
Mass number
nuclide
Atomic mass unit
Average atomic
mass
Mole
Avogadro’s number
Molar mass
2
Section 1
Atoms:
From Philosophical Idea
to
Scientific Theory
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
3
Foundation of Chemical Atomic Theory
• Law of Conservation of Mass
– Mass is neither created or destroyed
during ordinary chemical reactions or
physical changes
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
4
Law of Conservation OF
mass Animation
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
5
p. 69*
Law of Conservation of Mass Image
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
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p. 69*
Law of Conservation of Mass Image
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
7
Foundation of Chemical Atomic Theory
• Law of Conservation of Mass
Insert Holt Visualizing Matter Disk 1
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
8
Foundation of Chemical Atomic Theory
• Law of Definite Proportions
– A chemical compound contains the same
elements in exactly the same proportions
by mass regardless of the size of the
sample or the source of the compound.
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
9
Law of Definite Proportions
Animation
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
10
Foundation of Chemical Atomic Theory
• Law of Multiple Proportions
– If two or more different compounds are
composed of the same two elements then
the ratio of the masses of the second
element combined with a certain mass of
the first element is always a ratio of small
whole numbers.
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
11
Law of Multiple Proportions
Animation
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
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p. 69*
Law of Multiple Proportions Image
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
13
Foundation of Chemical Atomic Theory
• Law of Definite
Proportions
Insert Holt Visualizing Matter Disk 1
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
14
Dalton’s Atomic Theory
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
15
Dalton’s Atomic Theory
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
16
Dalton’s Atomic Theory
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
17
Dalton’s Atomic Theory
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
18
Dalton’s Atomic Theory
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
19
Modern Atomic Theory
Leucippus
Democritus
Atomic Theory
Tested by experiment and
modified with new discoveries
and experiments
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
20
Section 2
The Structure of the Atom
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
21
Cathode Ray Tube Animation
p. 72
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
22
Discovery of the Electron
• Cathode Ray Tube Experiment Thompson
• Observations
– Cathode Rays are deflected a magnetic
field.
– Cathode rays are deflected from a
negatively charged object.
– Charge to mass ratio is always the same
for the cathode rays.
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
23
Discovery of the Electron
• Cathode Ray Tube Experiment Thompson
• Conclusion
– Cathode rays are composed of
negatively charged particles
– Named “electrons”
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
25
Discovery of the Electron
• Oil Drop Experiment - Millikan
– Measured the charge of the electron
– Calculated the mass of an electron
• 9.109 x 10-31 kg
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
26
Oil Drop Experiment
Animation
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
27
Discovery of the Electron
• Inferences
–Atoms are neutral, so there must be a
positive charge.
–Electrons are small, so there must be
other particles.
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
28
Discovery of the Electron
• Plum Pudding Model
–Negative electrons were spread
evenly throughout the positive
charge.
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
29
Insert Glencoe Disk 1 and click on picture for animation.
Cloud Chamber Movie
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
30
Discovery of the Atomic Nucleus
• Gold Foil Experiment – Rutherford et. al
– Hypothesis: Alpha particles would pass
through with slight deflection.
– Observation: 1 in 8000 particles were
deflected back to the source.
– Conclusion: The atom contains a small
densely packed bundle of matter with a
positive charge
– Named the “nucleus”
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
31
Gold Foil Experiment
Animation
p. 72
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
32
p. 75
Gold Foil Experiment Image
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
35
Discovery of the Atomic Nucleus
Relative size of the nucleus
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
36
Composition of The Atomic Nucleus
• Nuclei contain protons and neutrons
• Neutral because number of protons equal
number of electrons
• Each element has a different number of
protons in their nucleus
– The number of protons determines the
atom’s identity
• Nuclear forces hold protons & neutrons
together
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
37
p. 76
Properties of Subatomic Particles
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
38
Nuclear Forces Image
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
39
Gold Foil Experiment Photo
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
40
Gold Foil Experiment Photo
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
41
Thompson and Rutherford Photo
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
42
Section 2 Homework
Ch 3 Sec 2 Review Page 76 #1-5
Chapter 3 Section 3 Counting
Atoms pages 77-87
43
Section 3
Counting Atoms
Chapter 3 Section 3 Counting
Atoms pages 77-87
44
Atomic Number
• The number of protons of each atom of
that element
• Identifies the element
Chapter 3 Section 3 Counting
Atoms pages 77-87
45
Isotopes
• Atoms of the same element that have
different masses
• Isotopes of hydrogen
– Protium 1p+ 0n0
– Deuterium 1p+ 1n0
– Tritium 1p+ 2n0
• Isotopes do not differ significantly in
their chemical behavior
Chapter 3 Section 3 Counting
Atoms pages 77-87
46
Mass Numbers
• Mass numbers = # of p+ + # of n0
of a specific isotope
• Examples
– Protium 1p+ + 0n0 = 1
– Deuterium 1p+ + 1n0 = 2
– Tritium 1p+ + 2n0 = 3
Chapter 3 Section 3 Counting
Atoms pages 77-87
47
Designating Isotopes
• Hyphen notation
– name of element – mass number
– Hydrogen – 3
• Nuclear symbol
mass number
atomic number
Chapter 3 Section 3 Counting
Atoms pages 77-87
48
Number of neutrons in an atom
neutrons = mass number – atomic number
Problem page 79
How many p+, e- and n0 are there in an
atom of chlorine-37?
17 p+ 17e- 20n0 (37-17)
Practice Problems page 80 #1-3
Nuclide – a general term for a specific
isotope of an element
Chapter 3 Section 3 Counting
Atoms pages 77-87
49
Relative Atomic Mass
• One atom, carbon-12, is set as a
standard
• All masses are expressed in relation to
this standard
• 1 atomic mass unit = 1/12 the mass of
a carbon-12 atom
Chapter 3 Section 3 Counting
Atoms pages 77-87
50
Relative Atomic Mass
• Examples
– Hydrogen – 1 = 1.007825 amu
– Oxygen – 16 = 15.994915 amu
– Magnesium – 24 = 23.985042 amu
• p+ = 1.007276 amu, n0 = 1.008665
amu, e- = 0.0005486 amu
• Relative mass and mass number are
close in value but not the same
Chapter 3 Section 3 Counting
Atoms pages 77-87
51
Average Atomic Mass
• The weighted average of the atomic
masses of the naturally occurring
isotopes of an element
• Example
– Copper
Cu-63: .6915 x 62.93 amu = 43.52
Cu-65: .3085 x 64.93 amu = 20.03
63.55 amu
Chapter 3 Section 3 Counting
Atoms pages 77-87
52
Average Atomic Mass Animation
Chapter 3 Section 3 Counting
Atoms pages 77-87
53
The Mole Animation
Chapter 3 Section 3 Counting
Atoms pages 77-87
54
The Mole
• An amount of a substance that contains
as many particles as there are atoms in
exactly 12 g carbon-12.
• Similar to a dozen or a pair or a gross
• 6.022 x 1023 carbon-12 atoms = 12
grams of carbon-12
• Avogadro’s number = 6.022 x 1023
particles
Chapter 3 Section 3 Counting
Atoms pages 77-87
55
Avogadro’s Number Animation
Chapter 3 Section 3 Counting
Atoms pages 77-87
56
Molar mass
• The mass of one mole of a pure
substance
• Unit = g/mol
• On the periodic table, use 4 sig. figs.
Chapter 3 Section 3 Counting
Atoms pages 77-87
57
Molar Mass Image
p. 83
Chapter 3 Section 3 Counting
Atoms pages 77-87
58
Gram-Mole Conversions
• The conversion factor for gram-mole
conversion is molar mass.
g
OR
mol
mol
g
• What is the mass, in grams, of 3.50
moles of Cu?
– 222 grams Cu
Chapter 3 Section 3 Counting
Atoms pages 77-87
59
Practice Problems page 85
p. 85
1. What is the mass in grams
the element iron?
2. What is the mass in grams
of the element potassium?
3. What is the mass in grams
of the element sodium?
4. What is the mass in grams
the element nickel?
Chapter 3 Section 3 Counting
Atoms pages 77-87
of 2.25 mol of
126 g Fe
of 0.357 mol
14.7 g K
of 0.0135 mol
0.310 g Na
of 16.3 mol of
957 g Ni
60
Conversions Image
p. 84
Chapter 3 Section 3 Counting
Atoms pages 77-87
61
Gram-Mole Conversions
• The conversion factor for gram-mole
conversion is molar mass.
g
OR
mol
mol
g
• A Chemist produced 11.9 g of Al. How
many moles of Al were produced?
– 0.411 moles Al
Chapter 3 Section 3 Counting
Atoms pages 77-87
62
Practice Problems page 85
p. 85
1. How many moles of calcium are in 5.00
g of calcium? 0.125 mol Ca
2. How many moles of gold are in 3.60 x
10-5 g of gold? 1.83 x 10-7 mol Au
3. How many moles of zinc are in 0.535 g
8.18 x 10-3 mol Zn
of zinc?
Chapter 3 Section 3 Counting
Atoms pages 77-87
63
Conversions with Avogadro’s Number
• The conversion factor for particle-mole
conversion is Avogadro’s number.
6.022x1023atoms
1 mol
1 mol
OR
6.022x1023atoms
• How many moles of silver are in 3.01 x
1023 atoms of silver
– 0.500 moles Ag
Chapter 3 Section 3 Counting
Atoms pages 77-87
64
Practice Problems page 86
1. How many moles of lead are 1.50 x 1012
atoms of lead? 2.49 x 10-12 mol Pb
2. How many moles of tin are in 2500
atoms of tin? 4.2 x 10-21 mol Sn
3. How many atoms of aluminum are in
2.75 mol of aluminum?
p. xx
1.66 x 1024 atoms Al
Chapter 3 Section 3 Counting
Atoms pages 77-87
65
Conversions with Avogadro’s Number
• The conversion factor for particle-mole
conversion is Avogadro’s number.
6.022x1023atoms
1 mol
1 mol
OR
6.022x1023atoms
• What is the mass, in grams, of
1.20x1018 atoms of Cu?
– 1.27 x 10-4 g Cu
Chapter 3 Section 3 Counting
Atoms pages 77-87
66
Practice Problems page 87
1. What is the mass in grams of 7.5 x 1015
atoms of nickel?7.3 x 10-7 g Ni
2. How many atoms of sulfur are in 4.00 g
7.51 x 1022 atoms S
of sulfur?
3. What mass of gold contains the same
number of atoms as 9.0 g of aluminum?
p. xx
66 g Au
Chapter 3 Section 3 Counting
Atoms pages 77-87
67
Conversions Image
p. 84
Chapter 3 Section 3 Counting
Atoms pages 77-87
68
Section 1 Homework
Section Review Page 87 #1-7
Chapter 3 Section 3 Counting
Atoms pages 77-87
69