Transcript Chemistry

Chapter 2
Atoms, Molecules, and Ions
The Early History of Chemistry
- Before 16th Century
Alchemy: Attempts (scientific or otherwise) to
change cheap metals into gold
- 17th Century
Robert Boyle: First “chemist” to perform
quantitative experiments
- 18th Century
George Stahl: Phlogiston flows out of a burning
material.
Joseph Priestley: Discovers oxygen gas,
“dephlogisticated air.”
Law of Conservation of Mass
- Discovered by Antoine Lavoisier
- Mass is neither created nor destroyed
- Combustion involves oxygen, not
phlogiston
Other Fundamental Chemical Laws
Law of Definite Proportion
- A given compound always contains exactly
the same proportion of elements by mass.
- Carbon tetrachloride is always 1 atom
carbon per 4 atoms chlorine.
Other Fundamental Chemical Laws
Law of Multiple Proportions
- When two elements form a series of
compounds, the ratios of the masses of the
second element that combine with 1 gram of
the first element can always be reduced to
small whole numbers.
- The ratio of the masses of oxygen in H2O
and H2O2 will be a small whole number
(“2”).
Dalton’s Atomic Theory (1808)
1 Each element is made up of tiny particles
called atoms.
2 The atoms of a given element are identical;
the atoms of different elements are
different in some fundamental way or
ways.
Dalton’s Atomic Theory
(continued)
3 Chemical compounds are formed when
atoms combine with each other. A given
compound always has the same relative
numbers and types of atoms.
4 Chemical reactions involve reorganization
of the atoms - changes in the way they are
bound together. The atoms themselves are
not changed in a chemical reaction.
Atomic Theory
Alpha, Beta, and Gamma
Movie
Early Experiments to
Characterize the Atom
- J. J. Thomson - postulated the existence of
electrons using cathode ray tubes.
- Ernest Rutherford - explained the nuclear
atom, containing a dense nucleus with
electrons traveling around the nucleus at a
large distance.
J. J. Thompson Experiment
02_21
Applied
electric field
(+)
(-)
Metal
electrode
(+)
(-)
Metal
electrode
Millikan Oil Drop Experiment
Movie
Plum Pudding Model
Rutherford Experiment
Movie
02_25
Electrons scattered
throughout
Diffuse
positive
charge
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-
-
-
-
-
-
-
n+
-
-
-
-
-
-
(a)
-
(b)
The Modern View of Atomic
Structure
The atom contains:
- electrons
- protons: found in the nucleus, they have a
positive charge equal in magnitude to the
electron’s negative charge.
- neutrons: found in the nucleus, virtually
same mass as a proton but no charge.
The Mass and Change of the
Electron, Proton, and Neutron
Particle
Mass (kg)
Charge
Electron
9.11  1031
1
27
Proton
1.67  10
Neutron
1.67  1027
1+
0
The Chemists’ Shorthand:
Atomic Symbols
Mass number 
Atomic number 
39
K
19
 Element Symbol
Isotopes
Periodic Table
Elements classified by:
- properties
- atomic number
Groups (vertical)
1A = alkali metals
2A = alkaline earth metals
7A = halogens
8A = noble gases
Periods (horizontal)
Noble
gases
02_29
Alkaline
1 earth metals
Halogens
1A
1
Alkali metals
H
18
8A
2
13
14
15
16
17
2A
3A
4A
5A
6A
7A
2
He
3
4
5
6
7
8
9
10
Li
Be
B
C
N
O
F
Ne
11
12
13
14
15
16
17
18
Na
Mg
Al
Si
P
S
Cl
Ar
3
4
5
6
7
8
9
Transition metals
10
11
12
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
55
56
57
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
Cs
Ba
La*
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
104
105
106
107
108
109
110
111
87
88
Fr
Ra
89
Ac†
Unq Unp Unh Uns Uno Une Uun Uuu
*Lanthanides
† Actinides
58
59
60
61
62
63
64
65
66
67
68
69
70
71
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
90
91
92
93
94
95
96
97
98
99
100
101
102
103
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
Fill in the Table
Chemical Bonds
The forces that hold atoms together in
compounds. Covalent bonds result from atoms
sharing electrons.
Molecule: a collection of covalently-bonded
atoms.
Methane
The Chemists’ Shorthand:
Formulas
Chemical Formula:
Symbols = types of atoms
Subscripts = relative numbers of atoms
CO2
Structural Formula:
Individual bonds are shown by lines.
O=C=O
Ions
Cation: A positive ion
Mg2+, NH4+
Anion: A negative ion
Cl, SO42
Ionic Bonding: Force of attraction between
oppositely charged ions.
Naming Compounds
Binary Ionic
Compounds:
1. Cation first, then anion
2. Monatomic cation = name of the element
Ca2+ = calcium ion
3. Monatomic anion = root + -ide
Cl = chloride
CaCl2 = calcium chloride
Type I – Binary Ionic Cmpds
Name the Following
Write the Symbols for
the Following
KI
Lithium Chloride
MgBr2
Barium Fluoride
SrO
Magnesium Oxide
Naming Compounds
(continued)
Binary Ionic Compounds (Type II):
-
metal forms more than one cation
use Roman numeral in name
PbCl2
Pb2+ is cation
PbCl2 = lead (II) chloride
Type II – Binary Ionic Cmpds
Name the followingCuO
Write the Formula for
the followingIron(III) Sulfate
Fe2O3
Zinc Oxide
CuF
Naming Compounds
(continued)
Binary compounds (Type III):
- Compounds between two nonmetals
- First element in the formula is named first.
- Second element is named as if it were an
anion.
- Use prefixes
- Never use mono-
P2O5 = diphosphorus pentoxide
Alkanes
02_31
Binary compound?
Yes
Metal present?
No
Yes
Type III:
Use prefixes.
Does the metal form
more than one cation?
No
Type I:
Use the element
name for the cation.
Yes
Type II:
Determine the charge of the cation;
use a Roman numeral after the
element name for the cation.
02_33
Does the anion
contain oxygen?
No
hydro + anion root
+ -ic
hydro (anion root)ic acid
Yes
Check the ending of the anion.
-ite
anion or element root
+ -ous
(root)ous acid
-ate
anion or element root
+ -ic
(root)ic acid
End