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Modern Chemistry Chapter 3 Atoms:
the building block of matter
2
Chapt
er voc
abular
y 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
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
3
Section 1 Atoms:
From Philosophical Idea to
Scientific Theory
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
4
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
5
Law of Conservation of Mass image p.
69
*
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
6
Law of Conservation of Mass image p.
69
*
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 De
finite
Prop
ortion
s An
imati
on
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
10
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
11
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
12
Law
of Mu
ltiple
Propo
rtions
An
imati
on
Chapter 3 Section 1 Atoms: Ideas
to Theory pages 67-71
13
Law of Multiple Proportions image p.
69
*
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 2 The Structure
of the Atom pages 72-76
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Section 2
The Structure of the Atom
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
21
Catho
de Ra
y Tub
e Anim
ation
p.
72
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
22
CaTHODE Ray Tube Movie Animation
Insert
Gle
ncoe D
isk 1
and c
lick o
n p
ictu
re for
anim
ation.
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
23
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
24
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 D
rop Ex
perim
ent
Anim
ation
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
Cloud Chamber Movie
Insert
Gle
ncoe D
isk 1
and c
lick o
n p
ictu
re for
anim
ation.
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 E
xperi
ment
Anim
ation
p.
72
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
34
Gold Foil Experiment Image p.
75
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
Properties of Subatomic Particles p.
76
Chapter 3 Section 2 The Structure
of the Atom pages 72-76
38
Nucle
ar Fo
rces I
mage
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 3 Counting
Atoms pages 77-87
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
Avera
ge At
omic
Mass
Anim
ation
Chapter 3 Section 3 Counting
Atoms pages 77-87
53
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
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The M
ole A
nimati
on
Chapter 3 Section 3 Counting
Atoms pages 77-87
55
Avog
adro’s
Num
ber A
nimati
on
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.
• What is the mass, in grams, of 3.50 moles of Cu?
– 222 grams Cu
OR g
mol g
mol
Chapter 3 Section 3 Counting
Atoms pages 77-87
59
Practice Problems page 85 1. What is the mass in grams of 2.25 mol of
the element iron?
2. What is the mass in grams of 0.357 mol of the element potassium?
3. What is the mass in grams of 0.0135 mol of the element sodium?
4. What is the mass in grams of 16.3 mol of the element nickel?
p. 85
126 g Fe
14.7 g K
0.310 g Na
957 g Ni
Chapter 3 Section 3 Counting
Atoms pages 77-87
60
Conv
ersion
s Ima
ge 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.
• A Chemist produced 11.9 g of Al. How many moles of Al were produced?
– 0.411 moles Al
OR g
mol g
mol
Chapter 3 Section 3 Counting
Atoms pages 77-87
62
Practice Problems page 85 1. How many moles of calcium are in 5.00
g of calcium?
2. How many moles of gold are in 3.60 x 10-5 g of gold?
3. How many moles of zinc are in 0.535 g of zinc?
p. 85
0.125 mol Ca
1.83 x 10-7 mol Au
8.18 x 10-3 mol Zn
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.
• How many moles of silver are in 3.01 x 1023 atoms of silver
– 0.500 moles Ag
OR 6.022x1023atoms
1 mol 6.022x1023atoms
1 mol
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. How many moles of tin are in 2500 atoms of tin?
3. How many atoms of aluminum are in 2.75 mol of aluminum?
p. xx
2.49 x 10-12 mol Pb
4.2 x 10-21 mol Sn
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.
• What is the mass, in grams, of 1.20x1018 atoms of Cu?
– 1.27 x 10-4 g Cu
OR 6.022x1023atoms
1 mol 6.022x1023atoms
1 mol
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?
2. How many atoms of sulfur are in 4.00 g of sulfur?
3. What mass of gold contains the same number of atoms as 9.0 g of aluminum?
p. xx
7.3 x 10-7 g Ni
7.51 x 1022 atoms S
66 g Au
Chapter 3 Section 3 Counting
Atoms pages 77-87
67
Conv
ersion
s Ima
ge p.
84
Chapter 3 Section 3 Counting
Atoms pages 77-87
68
Section 1 Homework
Section Review Page 87 #1-7