CHEM115 General Chemistry I
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Chapter Opener
2.1 Elements and
Atoms are Described by Dalton's Atomic Theory
2.2 Atoms are Composed of Subatomic
Particles
2.3 The Periodic Table is used to Organize and Correlate Facts
2.4 Elements can
be Metals, Nonmetals, or Metalloids
2.5 Formulas and Equations Describe Substances and
their Reactions
2.6 Molecular Compounds Contain Neutral Particles Called
Molecules
2.7 Ionic Compounds are Composed of Charged Particles called Ions
2.8 The
Formulas of Many Ionic Compounds can be Predicted
2.9 Molecular and Ionic Compounds
are Named following a System
Summary
Tools for Problem Solving
Questions,
Problems, and Exercises
Glossary
Office Hours Videos
Chapter 2, Problem 76
Chapter 2, Problem 83
Chapter 2,
Problem 99a
Chapter 2, Problem 99b
Chapter 2, Problem 99c
Chapter 2, Problem
104a Chapter 2, Problem 104b
Chapter 2, Problem 104c
Chapter 2, Problem
104d
Chapter 2, Problem 104e
Chapter 2, Problem 120a
Chapter 2, Problem
120b
Chapter 2, Problem 120c
Chapter 2, Problem 120d
Chapter 2, Problem
120e Chapter 2, Problem 120f
Chapter 2, Problem 120g
Chapter 2, Problem
129
Chapter 2, Problem 130
Chapter 2, Problem 132
Chapter 2, Problem 138
ChemFAQ
ChemFAQ - Chapter 2
Interactive LearningWare
2.86. Interactive LearningWare
2.88. Interactive
LearningWare
Video Demonstrations
Sodium and chlorine
Additional Resources
3D Molecules
Audio Pronunciation Guide
Ch 2. Elements,
Compounds and
Chemical Reactions
Brady &
Senese, 5th Ed.
Chemical Laws
• The law of conservation of mass - in a chemical
reaction, the mass of the reactants (starting
materials) will equal the mass of resulting
products
 Implication: reactions involve the re-organization of
materials.
• The law of definite proportions- the ratio of
masses of each element is fixed for a given
compound
 Implication: Each atom has a fixed specific mass, thus
in unique combinations, the mass ratio is specific
2.1. Elements and atoms are described by Dalton’s atomic theory
3
Learning Check:
Magnesium burns in oxygen to form
magnesium oxide. If 16.88 g of Mg are
consumed and 28.00 g of MgO are produced,
what mass of oxygen was consumed?
2.1. Elements and atoms are described by Dalton’s atomic theory
4
Question:
Two compounds of copper and chlorine
exist with one having twice as much
chlorine per gram of copper as the
other. This is evidence of which law?
a: Conservation of Mass
b: Definite Proportions
c: Multiple Proportions
Dalton’s Atomic Theory
•
•
Matter consists of tiny particles called atoms
Atoms are indestructible. In chemical reactions, the
atoms rearrange but they do not themselves break
apart
+
2.1. Elements and atoms are described by Dalton’s atomic theory
6
Dalton’s Atomic Theory (Cont.):
•
•
•
In any sample of a pure element, all the atoms
are identical in mass and other properties.
The atoms of different elements differ in mass
and other properties.
In a given compound the constituent atoms are
always present in the same fixed numerical
ratio.
NaCl has a 1:1 atom ratio on the atomic
level and larger
2.1. Elements and atoms are described by Dalton’s atomic theory
7
John Dalton
Learning Check:
In a sample of MgO, there are 16.89 g Mg and
11.11 g O. What mass of O would there be
in a sample that contains 2.00 g of Mg?
2.1. Elements and atoms are described by Dalton’s atomic theory
9
Your Turn!
In a sample of an unknown compound, the mass
ratio of Cl to C is 47.227g Cl to 4.00 g C. In
another sample, there are 0.553 g of Cl. What
mass of C would be in this sample?
A.
0.1532 g
B.
6.52 g
C.
0.153 g
D.
0.0468 g
E.
None of these
2.1. Elements and atoms are described by Dalton’s atomic theory
10
Question:
9 grams of water contain 1 gram of
hydrogen. How many grams of water
contain 3 grams of hydrogen?
a: 1/3 gram
b: 3 grams
c: 9 grams
d: 27 grams
The Law Of Multiple Proportions
When two elements form more than one compound,
the different masses of one element that combine
with the same mass of the other element are in the
ratio of small whole numbers.
• cements the idea that atoms react as complete
(whole) particles.
• chemical formulas indicate whole numbers of
atoms- not fractions
2.1. Elements and atoms are described by Dalton’s atomic theory
12
Using The Law Of Multiple Proportions
sulfur
sulfur
dioxide
trioxide
Mass S
32.06 g
32.06 g
Mass O
32.00 g
48.00 g
Use these data to prove the law of
multiple proportions
2.1. Elements and atoms are described by Dalton’s atomic theory
13
Your Turn!
Two substances are formed from A and B. AB and
A2B3. If the mass ratio of A/B in AB is 3.49,
what is the ratio of A/B in A2B3?
A. 0.431
B. 3.49
C. 0.286
D. 2.33
E. not enough information given
2.1. Elements and atoms are described by Dalton’s atomic theory
14
Proof Of Atoms
• Since the early 1980’s, the Scanning Tunneling
Microscope (STM) has been used
• A surface can be scanned for topographical
information
• The image for all matter shows spherical regions of
matter-- atoms
Atomically resolved STM image of clean Au(100). This image is mad
2.1. Elements and atoms are described by Dalton’s atomic theory
15
Radioactivity
• One of the pieces of evidence for the
fact that atoms are made of smaller
particles came from the work of
Marie Curie (1876-1934).
• She discovered radioactivity, the
spontaneous disintegration of some
elements into smaller pieces.
Cathode Ray Tube (CRT)
A gas filled glass tube that has electrical charge
applied at both ends.
Such a tube glows with light and is the precursor of
the modern-day television screen.
2.2 Atoms are composed of subatomic particles
17
Discovery Of The Electron By JJ Thomson
• In 1897, Thomson placed a
magnet near CRT and noted
deflection of the beam
• Repeated experiment with an
electrical field and noted that
the discharge was deflected by
an electrical field toward the
(+) plate
• Announced discovery of (-)
particle, later named “electron”
by Stoney
2.2 Atoms are composed of subatomic particles
18
Determining The Charge On An e-: Millikan
2.2 Atoms are composed of subatomic particles
19
Rutherford’s Alpha Scattering Experiment
Most alpha rays passed right through the Au
A few were deflected off at an angle
1 in 8000 bounced back towards the alpha ray source
2.2 Atoms are composed of subatomic particles
21
Rutherford’s Nuclear Model of the Atom
• Since most of the alpha particles were not
deflected, most of the atom is empty space.
• Since some of the particles were deflected,
they encountered small particles of the
same charge.
• Since some particles were reflected, there
must be a small dense area.
2.2 Atoms are composed of subatomic particles
22
The modern view of the atom was
developed by
Ernest
Rutherford (1871-1937).
“It was about as credible as if
you had fired a 15-inch
artillery shell at a piece of
paper and it came back and
hit you”
02m11an1.mov
Question:
Discovery Of The Proton
• Discovered in 1918 in Ernest Rutherford’s lab
• Detected using a Mass Spectrometer
2.2 Atoms are composed of subatomic particles
25
Discovery Of The Neutron
• Chadwick determined that the nuclei of
light atoms could be caused to
disintegrate by being bombarded by
alpha particles.
• In collision of alpha particles with Be, a
free neutron was created
• the presence of the neutron confirmed in
1932
2.2 Atoms are composed of subatomic particles
26
Subatomic Particles
Particle
electron
proton
neutron
Symbol
0
1
1
1
1
0
e or e
-
p or 11H 
n or n
0
Mass (u)
Location Charge
5.48579903(10-4)
orbital
1-
1.007276470
nucleus
1+
1.008664904
nucleus
0
2.2 Atoms are composed of subatomic particles
27
Atomic Mass
• Dalton’s atomic theory states that atoms of an
element have a constant, characteristic atomic mass
or atomic weight measured in amu (u)
• Atomic masses are based on a standard mass, that of
an atom of C
• 1 atom of Carbon-12 = 12 u
• Thus 1 u = 1/12 the mass of a Carbon-12 atom
2.2 Atoms are composed of subatomic particles
28
Isotopes
• Most elements in nature are uniform mixtures of two
or more kinds of atoms with slightly different masses
• Atoms of the same element with different masses are
called isotopes
 For example: there are 3 isotopes of hydrogen and 4
isotopes of iron
• Chemically, isotopes have virtually identical
properties
2.2 Atoms are composed of subatomic particles
29
Atomic Notation
A
Z
Sy
• An element is a substance whose atoms all contain
the identical number of protons, called the atomic
number (Z)
• Isotopes are distinguished by mass number (A):
 Atomic number, Z = number of protons
 Mass number, A = (number of protons) + (number of
neutrons)
 Note that for atoms, A is greater than Z: the symbol is topheavy
• For charge neutrality, the number of electrons and
protons must be equal
2.2 Atoms are composed of subatomic particles
30
Example: uranium-235
Mass number, A (protons + neutrons)  235
Chemical Symbol

U
Atomic number, Z (number of protons)  92
This information can be summarized:
 Number of protons = 92 ( = number of electrons)
 Number of neutrons = 143
 Atomic number (Z) = 92
 Mass number (A) = 92 + 143 = 235
 Chemical symbol = U
2.2 Atoms are composed of subatomic particles
31
Question:
How many neutrons are there in an
atom of sulfur-33?
a: 16
b: 17
c: 33
d: 49
Question:
How many electrons are there in an
atom of uranium-238?
a: 92
b: 146
c: 238
d: 330
Question:
Learning Check:
Fill in the blanks:
symbol
neutrons
60Co
protons
electrons
29
29
81Br
36
2.2 Atoms are composed of subatomic particles
35
Your Turn!
How many neutrons are there in 52Fe?
A. 52
B. 55
C. 26
D. none of these
2.2 Atoms are composed of subatomic particles
36
What is the total value of:
3 quarters, two dimes and one nickel?
Learning Check: Atomic Mass
Naturally occurring chlorine is a mixture of two
isotopes. In every sample of this element, 75.77% of
the atoms are chlorine-35 and 24.23% are chlorine37. The measured mass of chlorine-35 is 34.9689 u
and that of chlorine-37 is 36.9659 u. Calculate the
average atomic mass of chlorine.
2.2 Atoms are composed of subatomic particles
38
Your Turn
There are 2 isotopes of element Z. The first is
56.5% in abundance and has a mass of 152.3 u. If
the atomic mass is 155.5 u, what is the mass of
the other isotope?
A. 156 u
B. 44.5 u
C. 157. u
D. not enough information given
E. none of these
2.2 Atoms are composed of subatomic particles
39
Question:
Copper has two stable isotopes, copper-63
and copper-65. What is the abundance
of copper-65?
a: 5.75%
b: 27.5%
c: 50%
d: 72.5%
e: 95.5%
Question:
Problem Solving
Calculate the average atomic mass of chromium
of naturally occurring chromium based on the
information given for its four isotopes:
4.31% 50Cr of mass 49.946 amu,
83.76% 52Cr of mass 51.941 amu,
9.55% 53Cr of mass 52.941 amu and
2.38% 54Cr of mass 53.939 amu.
Problem Solving
Naturally occurring Gallium consists of two
isotopes. Calculate the percent abundances of
Ga-69 and Ga-71 when the atomic mass is 69.72
amu and the isotopic masses are 68.926 and
70.925 amu respectively
Periodic Table
1A
2A
1
H
3
4
Li
Be
11
12
Na
arranged in numbered rows –
“periods”
columns called “groups” or
“families”
M
g3B
4B
5B
6B
7B
8B
8B
8B
1B
2B
3A
4A
5A
6A
7A
8A
2
He
5
6
7
8
9
10
B
C
N
O
F
Ne
13
14
15
16
17
18
Al
Si
P
S
Cl
Ar
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
87
88
89
104
105
106
107
108
109
110
111
112
114
Fr
Ra
Ac
Rf
Db
Sg
Bh
Hs
Mt
Ds
Uuu
Uub
Uuq
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
2.3. The periodic table is used to organize and correlate facts
44
Periodic Table
• Summarizes chemical and physical properties of the
elements
• Mendeleev first arranged atoms by increasing atomic
mass. Noted repeating (periodic) properties
• Modern table is arranged by increasing atomic
number (Moseley)
2.3. The periodic table is used to organize and correlate facts
45
Some Important Classifications:
• A groups = representative elements or main group
elements
I A = alkali metals
VII A = halogens
II A = alkaline earth metals
VIII = noble (also inert) gases
• B groups = transition elements
• Inner transition elements = elements 58 – 71 and 90
– 103
58 – 71 = lanthanide elements
90 – 103 = actinide elements
2.3. The periodic table is used to organize and correlate facts
46
The modern periodic table
2.3. The periodic table is used to organize and correlate facts
47
Metals, Nonmetals, And Metalloids
2.4. Elements can be metals, non-metals, or metalloids
48
Your turn!
Which of the following is correct?
A. Cu is a representative transition element
B. Na is an alkaline earth metal
C. Al is a semimetal in group IIIa
D. F is a representative halogen
E. None of these are correct
2.4. Elements can be metals, non-metals, or metalloids
49
Properties Of Metals
• reflect light (have metallic luster)
• Can be hammered or rolled into thin sheets (are
malleable) and can be drawn into wire (are ductile)
• Are solids at room temperature (except Hg)
• conduct electricity and heat
2.4. Elements can be metals, non-metals, or metalloids
50
Nonmetals And Metalloids
• Nonmetals




Lack the properties of metals
Tend to pulverize when struck with a hammer
Non-conductors of electricity and heat
Many are gases, a few solids, and one liquid
(Br)
 React with metals to form (ionic) compounds
• Metalloids
 Have properties between metals and nonmetals
2.4. Elements can be metals, non-metals, or metalloids
51
Question:
Which is a fourth-period alkaline
earth metal?
a: K
b: Ca
c: Zr
d: C
e: Sn
Question:
Which are almost always found in nature in
pure elemental form?
a: alkali metals
b: inner transition metals
c: noble gases
d: halogens
e: metalloids
Question:
Which is not a characteristic property of
most metals?
a: malleability
b: good electrical conductivity
c: ductility
d: poor heat conductivity
e: luster
Question:
Which describes a physical property?
a: colorless
b: flammable
c: toxic
d: reactive
e: corrosive
Question:
www.americanbonanza.com
Question:
Question:
Question:
www.luxfer.com
Chemical Formulas
• Are symbols used to describe other elements in a
compound
• elements and compounds
• Free elements are not combined with another
element in a compound. Examples: Fe (iron), Na
(sodium), and K (potassium)
 Many non-metals occur in groups of 2 (as diatomic
molecules)- H, O, N, F, Cl, I, Br
 Some elements occur as molecules: P4, S, S8, P10, O3 ,
etc…
2.5. Formulas and equations describe substances and their reactions
60
Chemical Formulas (Cont.)
• Specify the composition of a substance
• Fe2O3 is composed of the elements iron and oxygen
in a 2:3 ratio
• CO(NH2)2 expands to CON2H4, but parentheses
often group atoms to show the compound’s
structure
2.5. Formulas and equations describe substances and their reactions
61
MOLECULAR FORMULAS
• Formula for glycine is C2H5NO2
• In one molecule there are
 2 C atoms
 5 H atoms
 1 N atom
 2 O atoms
Question:
How many atoms of hydrogen are present in the
formula
(NH4)2HPO4?
a: 5
b: 6
c: 7
d: 9
e: none of these
Hydrates
• Hydrates are crystals that contain water
molecules, for example plaster: CaSO4 • 2H2O
 When all the water is removed (by heating), the solid
that remains is said to be anhydrous (without water)
CuSO4 •5H2O
2.5. Formulas and equations describe substances and their reactions
CuSO4
64
Learning Check:
Count The Atoms In A Chemical Formula
•
•
•
•
•
Na2CO3
(NH4)2SO4 •
Mg3(PO4)2 •
CuSO4•5H2O •
___Na, ___ C, ___ O
___N, ___H, ___S, ____O
___Mg, ___P, ____O
___Cu, ___S, ___O, ___H
2.5. Formulas and equations describe substances and their reactions
65
Chemical Equations
• 2 HCl(aq) + CaCO3(s)  CaCl2(aq) + H2O(l) +CO2(g)
 HCl and CaCO3 are called reactants
 CaCl2, H2O,CO2 are called the products
 Reactants are separated from products with “”
that means “yields”
• States matter: for solids use (s), liquids (l), gases (g),
and for substances dissolved in water (aqueous
solutions) use (aq).
• We will learn later that the behavior of the reactants
differs based on their states!
2.5. Formulas and equations describe substances and their reactions
66
Problem Solving
How many atoms are represented in each
of the following expressions:
a) 3N2O
b) 2(NH4)2CO3
c) BaSO3
d) CuSO4•2H2O
e) (NH4)3PO4
f) Sn(SCN)2
g) MgSO4•5H2O
Balanced Equations
• The number of atoms of each
type must remain the same on
each side of the arrow
• subscripts must not changethey define the identity of the
substances
• Coefficients- numbers in front
of formulas-- indicate the
number of molecules of each
type
• Balancing achieved by
adjusting coefficients
2 H2 + O 2
→2 H2O
2.5. Formulas and equations describe substances and their reactions
68
Balanced Equations
Note that the number of each type of atom balances
and that the coefficient applies to the entire formula
2.5. Formulas and equations describe substances and their reactions
69
Guidelines for Balancing Equations:
1) Balance elements other than H and O first
2) Balance as a group any polyatomic ions that
appears unchanged on both sides of the arrow
3) Balance separately those elements that appear
somewhere by themselves
•
As a general rule you should use the smallest
whole-number coefficients when writing
balanced chemical equations
Balancing
Equations
__C3H8(g) + __ O2(g) 
__CO2(g) + __ H2O(g)
__B4H10(g) + __ O2(g) 
_ B2O3(g) + __H2O(g)
04m04an1.mov
Balancing Equations
N 2O 5 
N 2O 4 +
NH4NO2 
KOH +
NH3 +
N2 +
H3PO4 
CuO 
O2
H2O
K3PO4 +
Cu +
N2 +
H2O
H2O
Question:
Which equation is balanced?
a: P4+ F2  PF5
b: H2 + S8  H2S
c: H2 + O2  H2O2
d: Li + O2  Li2O
Molecules Form When Nonmetallic Elements
Combine
• Molecules are neutral
particles made of 2 or more
atoms.
• Many molecular compounds
contain hydrogen:
Group
Period IVA
VA
VIA
2
CH4
NH3
H2O
3
SiH4
PH3
H2S
4
GeH4 AsH3
H2Se
5
SbH3
H2Te
VIIA
HF
HCl
HBr
HI
Noble
Gas
Ne
Ar
Kr
Xe
2.6 Molecular compounds contain neutral particles called molecules
74
Alkanes
• Alkanes are
hydrocarbons (contain
only C and H)
• Always have a ratio of
atoms CnH2n+2
• Named using a prefix
designating the
number of C
• All have –ane suffix.
C
1
2
3
4
5
6
7
8
9
10
Prefix
MethEthPropButPentHexHeptOctNonDec-
Suffix
Name
Methane
Ethane
Propane
+ane
2.6 Molecular compounds contain neutral particles called molecules
75
• Organic chemistry is a major specialty that deals
with compounds containing mostly carbon and
hydrogen
• Hydrocarbons contain only hydrogen and carbon
and are organic compounds
• Alkanes are the simplest hydrocarbons
1 = meth General formula is CnH2n+2
2 = eth3 = prop4 = but-
5 = pent6 = hex-
Learning Check: Name that alkane
2.6 Molecular compounds contain neutral particles called molecules
77
Your turn!
Which of the following is heptane?
A. C6H12
B. C7H14
C. C6H14
D. C7H16
Your turn!
Which is the correct name for C4H10?
A. methane
B. ethane
C. propane
D. pentane
E. none of these
Other Organic Compounds
Alkenes- hydrocarbons with fewer H than the
alkanes. CnH2n. Use the same prefixes, but
have the suffix -ene.
 C2H4 : ___________
 C3H6: _____________
2.6 Molecular compounds contain neutral particles called molecules
80
Other Organic Compounds (Cont.)
Alcohols- Replace one H in an alkane with an OH group
• Same prefixes, suffix becomes –anol
 CH3OH is ____________
 C2H5OH is _______________
2.6 Molecular compounds contain neutral particles called molecules
81
Your Turn!
What is the name of CH3CH2CH2CH2OH?
A. butanol
B. propanol
C. pentanol
D. tetranol
E. none of these
Your Turn!
What is a formula for heptene?
A.
B.
C.
D.
E.
C6 H12
C7H14
C6H14
C7H16
none of these
Question:
What is the formula for hexanol?
www.brynmawr.edu
A.
B.
C.
D.
C6H14
C6H13OH
C6H12OH
C6(OH)14
Ionic Compounds
• Positively charged ions are called cations
• Negatively charged ions are called anions
• subscripts in the formula always specify the
smallest whole-number ratio of the ions
needed to make a neutral combination
(formula unit)
2 Fe3+
3 O2-
Fe2O 3
2.7 Ionic compounds are composed of charged particles called ions
85
What About Ions?
•
•
•
•
Number of p+ = number of e- if neutral
Number of p+ < number of e- if negative
Number of p+ > number of e- if positive
The number of p+ never changes when ions form
How does Ca form Ca2+?
How is N3- formed?
2.7 Ionic compounds are composed of charged particles called ions
86
Learning Check:
Fill in the blanks:
Symbol
neutrons
60Co3+
protons
electrons
29
27
81Br-
36
2.7 Ionic compounds are composed of charged particles called ions
87
Question:
How many electrons are there in P3-
a: 12
b: 15
c: 18
d: 28
e: 34
Question:
How many protons are in Rb+
a: 36
b: 37
c: 38
d: 85
e: none of these
METALS
Group A metals:
charge=group#
Na+
Mg2+
Al3+
Transition metals have variable charges
Stock System indicates charge
Iron(III) means Fe3+
NONMETALS
Charge = 8-Group#
C4- carbide
N3- nitride
O2- oxide
F- fluoride
Charges on Common Ions
+1
+2
-4 -3 -2
+3
-1
Ionic Compounds Are Neutral
• The positive charge
must balance the
negative charge
• We could use trial and
error to find the least
common charge
+
-
+
-
2.8 The formulas of many ionic compounds can be predicted
+
-
93
Determining The Formula Of An Ionic
Compound
• Practically, we can often accomplish this by making the charge
magnitude (not the charge) of one ion into the subscript for the
other. (The “Criss-cross” rule)
• If you choose this approach, make sure that the subscripts are
reduced to the lowest whole number.
Al3+ O2Mg2+ O2NH4+ PO43-
2.8 The formulas of many ionic compounds can be predicted
94
Your Turn!
Which of the following is the correct formula for the
formula unit composed of potassium and oxygen
ions?
A. KO
B. KO2
C. K2O
D. none of these
Your Turn!
Which of the following is the correct formula for the
formula unit composed of Fe3+ and sulfide ions?
A. FeS
B. Fe3S2
C. Fe2S3
D. none of these
Transition And Post-transition Metals Usually Have
Multiple Charges
Transition Metals
Chromium
Cr2+, Cr3+
Manganese
Mn2+, Mn3+
Iron
Fe2+, Fe3+
Cobalt
Co2+, Co3+
Nickel
Ni2+
Copper Cu+, Cu2+
Post-transition Metals
Tin
Sn2+, Sn4+
Bismuth
Bi3+
Zinc Zn2+
Silver Ag+
Cadmium Cd2+
Gold Au+, Au3+
Mercury Hg22+, Hg2+
Lead
Pb2+, Pb4+
2.8 The formulas of many ionic compounds can be predicted
97
Some Polyatomic Ions
(Ions With Two Or More Atoms):
NH4+
Ammonium ion
CO32-
carbonate ion
OH-
hydroxide ion
H3O+
hydronium ion
NO2-
nitrite ion
SO32-
sulfite ion
NO3-
nitrate ion
SO42-
sulfate ion
ClO2-
chlorite ion
CrO42-
chromate ion
ClO3-
chlorate ion
Cr2O72- dichromate ion
PO43-
phosphate ion
2.8 The formulas of many ionic compounds can be predicted
98
The Stock System Of Naming Ionic Compounds
• Cations:
 If the metal forms only one positive ion, the cation
name is the English name for the metal
 If the metal forms more than one positive ion, the
cation name is the English name followed, without a
space, by the numerical value of the charge written as
a Roman numeral in parentheses
• Anions:
 monatomic anions are named by adding the “–ide”
suffix to the stem name for the element
 polyatomic ions use the names in Table 2.5
2.9 Molecular and ionic comounds are named following a system
99
Question:
What is the chemical formula of the ionic
compound formed by aluminum and nitrogen?
a: AlN
b: Al3N3
c: Al3N2
d: Al2N3
www.rpi.edu
Name the following compounds
•
•
•
•
•
•
K2S
NiSO4
CoF3
(NH4)3PO4
MoBr3
Pb(NO2)4
Problem Solving
Write the formula:
• Potassium chloride
• Calcium oxide
• Aluminum hydride
• Tin(II) bromide
• Copper(I) iodide
• Calcium chlorite
Question:
What is the formula of the ionic compound
formed by ammonium ion and phosphate ion?
a: NH4P
b: NH4PO4
c: (NH4)3P
d: (NH4)3PO4
e: NH4(PO4)3
www.agrium.com
Question:
What is the formula of copper(II) sulfate?
a: CuS
b: Cu2S
c: Cu2SO4
d: CuSO4
w1tp.com
Question:
What is the name of
NaC2H3O2 • 3H2O?
a: sodium carbonate hydrate
b: sodium carbonate trihydrate
c: sodium acetate hydrate
d: sodium acetate trihydrate
e: sodium hydrogen carbonate trihydrate
Chemicalforums.com
In BINARY COUMPOUNDS: first element by English
name, the second by appending the suffix –ide to its stem.
Greek letter for each indicates number
Chemical
Symbol
O
S
N
P
F
Cl
Br
I
Name as
Stem
First Element
oxoxygen
sulfsulfur
nitrnitrogen
phosph- phosphorus
fluorfluorine
chlorchlorine
brombromine
iodiodine
Name as
Second Element
oxide
sulfide
nitride
phosphide
fluoride
chloride
bromide
iodide
Then use prefix…
Greek prefixes indicate number of each atom in binary
molecular compounds
Greek Prefixes
mono- = 1 (often omitted)
di=2
tri=3
tetra- = 4
penta- = 5
Examples:
PF5
= phosphorus pentafluoride
HCl = hydrogen chloride
N2O5 = dinitrogen tetraoxide
hexa- = 6
hepta- = 7
octa= 8
nona- = 9
deca- = 10
Note: many
compounds have
common names, like
water for H2O.
Ban DiHydrogen Oxide
http://www.gopetition.com
Dihydrogen monoxide (DHMO) is colorless, odorless, tasteless, and kills uncounted
thousands of people every year. Most of these deaths are caused by accidental inhalation
of DHMO, but the dangers of dihydrogen monoxide do not end there. Prolonged exposure
to its solid form causes severe tissue damage.
Symptoms of DHMO ingestion can include excessive sweating and urination, and
possibly a bloated feeling, nausea, vomiting and body electrolyte imbalance. For those
who have become dependent, DHMO withdrawal means certain death.
Dihydrogen monoxide:
•
•
•
•
•
•
•
is also known as hydroxl acid, and is the major component of acid rain
contributes to the "greenhouse effect.“
may cause severe burns.
contributes to the erosion of our natural landscape.
accelerates corrosion and rusting of many metals.
may cause electrical failures and decreased effectiveness of automobile brakes.
has been found in excised tumors of terminal cancer patients.
Name the following compounds
• ClO3
• NF3
• HI
• BBr3
• N2O5
Question:
What is the name of SF4 ?
a: sulfur fluoride
b: monosulfur tetrafluoride
c: monosulfur tetrafluorine
d: sulfur tetrafluoride
e: sulfur tetrafluorine
genchem.chem.wisc.edu
Question:
What is the formula of tetraphosphorus
decaoxide?
a: PO10
b: P4O2
c: P4O10
d: 4PO10
e: 40 PO
2.9 Molecular and ionic comounds are named following a system
113
Learning Check: Name The Following
•
•
•
•
•
•
Na2O
K2O
NH4ClO3
Mg(C2H3O2)2
Cr2O3
ZnBr2
2.9 Molecular and ionic comounds are named following a system
114
Overview: Molecules vs. Formula Units
• electrically neutral, discrete particles called
molecules
• Neutral groups of charged particles called
formula units
115
Summary of Properties
Hardness and brittleness
Molecular compounds tend to be soft and easily crushed because the
attractions between molecules are weak and molecules can slide past
each other
Ionic compounds are hard and brittle because of the strong
attractions and repulsions between ions
Electrostatic Forces
The oppositely charged ions in ionic compounds are
attracted to one another by ELECTROSTATIC
FORCES.
These forces are governed by COULOMB’S LAW.
Melting points
To melt the particles in the solid must have sufficient
kinetic energy to overcome the attractions between
particles
Molecular compounds tend to have weak attractions
between particles and so tend to have low melting points
Many molecular compounds are gases at room
temperature
Ionic compound tend to have strong attractions so they
have high melting points
Nearly all ionic compounds are solids at room
temperature
Importance of Coulomb’s Law
NaCl, Na+ and Cl-,
m.p. 804 oC
MgO, Mg2+ and O2m.p. 2800 oC
Electrical conductivity requires the
movement of electrical charge
• Ionic compounds:
 Do not conduct electricity in the solid
state
 Do conduct electricity in the liquid
state
The ions are free to move in the liquid
state
• Molecular compounds:
 Do not conduct electricity in the solid
or liquid state
 Molecules are comprised of uncharged
particles
Question:
A clear, colorless solid is brittle and conducts electricity
when molten but not when solid. Is this solid a sample
of an ionic or covalent compound?
a: ionic
b: molecular
c: it’s equally likely to be either ionic or
molecular
d: it’s impossible to tell without additional
information
Question:
Question:
CuSO4 • 5H2O
Question:
www.crystalgrowing.com
Question:
www.aecc.ru
Question:
cavemanchemistry.com
Question:
Question:
Question:
In general, are the melting points of
molecular compounds higher or lower
than those of ionic compounds?
a: higher
b: lower