Chapter 2
Atoms, Ions, and Compounds
The Composition of Compounds
• The law of multiple proportions states
that the masses of element Y that
combine with a fixed mass of elements
X to form two or more different
compounds are in the ratios of small
whole numbers.
• Examples: NO, NO2, N2O, N2O5, etc.
Atomic Structure
• J. J. Thomson discovered the subatomic
particle know as the electron.
• Thomson used cathode ray tube.
Mass of An Electron
• Robert Millikan
determined the
mass of an
electron with his
oil-droplet
experiment.
Thomson Model of the Atom
• J. J. Thomson’s Plum-pudding model of the atom.
Radioactivity and the Nuclear Atom
HISTORY
• Henri Becquerel discovered that some
samples produced invisible radiation.
• One type is a steam of beta () particles
(high energy electrons).
• A second type consists of alpha ()
particles, which have a +2 charge and a
mass equivalent to that of a helium
nucleus.
Identification of Radiation
Penetrating Effects
Nuclear Chemistry
• Nuclear chemistry is the study of reactions that
involve changes in the nuclei of atoms.
• Radioactive decay is the spontaneous
disintegration of alpha, beta, and gamma
particles.
Rutherford’s Experiment
• Rutherford and two of his students
bombarded a thin foil of gold with  particles
to test Thomson’s model of the atom.
• Theory would predict that the  particles
would travel through the foil without
deflection, but the results didn’t confirm the
model.
Rutherford’s Experiment
The Nuclear Atom
• The nucleus of an atom contains all the
positive charge and nearly all the mass in an
atom.
• The nucleus is about 1/10,000 the size of the
atom.
• A proton is a positively charged subatomic
particle present in the nucleus of an atom.
The Third Subatomic Particle
• A neutron is an electrically neutral or
uncharged subatomic particle found in the
nucleus of an atom.
• Atomic Mass Units (amu) comprise a relative
scale used to express the masses of atoms
and subatomic particles.
• The scale is based on the definition that the
mass of 1 atom of carbon with 6 protons and
6 neutrons in its nucleus is exactly 12 amu.
Aston’s Experiment
• Francis W. Aston built a postive-ray analyzer.
• Data from neon gas samples demonstrated
that two different kinds of atoms or isotopes
existed.
• Isotopes are atoms of an element whose
nuclei have the same number of protons but
different numbers of neutrons.
Aston’s Positive-ray Analyzer
Symbols of Isotopes
• Each element consists of atoms with the
same number of protons in the nucleus. This
number is called atomic number (Z).
• Protons and neutrons in atomic nuclei are
called nucleons.
• The mass number (A) is the total number
nucleons in one atom of an element.
Writing the Symbol of an Isotope
A
Z
X
• A is the mass number
• Z is the atomic number
• X is the atomic symbol
Average Atomic Masses
• A mass spectrometer is an instrument that
measures precise masses and relative
amounts of ions of atoms and molecule.
• The natural abundance of an isotope is its
relative proportion among all the isotopes
found a natural sample.
• The average atomic mass of an element is
calculated by multiplying the natural
abundance of each isotope by its exact mass
in atomic mass units and then summing these
products.
Example
Neon is found in three isotopes in nature.
Isotope
Mass (amu)
Natural abundance (%)
Neon-20
19.9924
90.4838
Neon-21
20.99395
0.2696
Neon-22
21.9914
9.2465
Example
Neon is found in three isotopes in nature.
Isotope
Mass (amu)
Natural abundance (%)
Neon-20
19.9924
90.4838
Neon-21
20.99395
0.2696
Neon-22
21.9914
9.2465
19.9924 x 0.904838 =
20.99395 x 0.002696 =
21.9914 x 0.092465 =
18.0898323 amu
0.056599689 amu
2.033434801 amu
20.1797 amu
Mendeleev’s Periodic Table
• Dmitrii I. Mendeleev
arranged elements in
the periodic table by
their chemical and
physical properties.
• He left open spaces in
his periodic table to
account for elements
not yet discovered.
The Modern Periodic Table
• The modern periodic table is also based on a
classification of elements in terms of their
physical and chemical properties.
• The horizontal rows are called periods.
• Columns contain elements of the same family
or group.
• Transition metals are the elements in group 3
through 12 in the periodic table.
Groups of Elements
• Group 1 contains the alkali metals.
• Group 2 contains the alkaline earth
metals.
• Group 17 contains the halogens.
Broad Categories of Elements
• Metals are elements on the left-hand side of
the table.
 Metals are shiny solids that conduct heat and
electricity well and are malleable and ductile.
• Nonmetals have properties opposite to those
of the metals and are on the right side of
table
• Metalloids are the elements between the
metals and nonmetals.
Continued
• Main group elements or
representative elements are the
elements in groups 1,2 and 13 through
18.
• The noble gases are the elements in
Group 18.
Kinds of Compounds
• Molecular Compounds are composed of
atoms held together by covalent bonds.
• Covalent bonds are shared pairs of
electrons that chemically bond atoms
together.
• Ionic Compounds are composed of
positively and negatively charged ions that
are held together by electrostatic attraction.
• Ions with negative charge are called anions.
• Ions with positive charge are called cations.
Continued
• Molecular compounds are made of
nonmetals
• Ionic compounds are made of a metal and
a nonmetal.
• Metal form cations and nonmetals form
anions.
Ionic Compounds
Ionic compounds do not exist as discrete molecules. Instead they
exist as crystals where ions of opposite charges occupy
positions known as lattice sites.
Ions combine in the ratio that
results in zero charge to form
ionic compounds.
Since there is almost and
infinite number of ions in a
crystal lattice, then the
smallest ratio, called the
formula unit, is used to
describe an ionic compound
Crystal Lattice of NaCl
Terms
• Molecular formulas describe the exact
number and type of atoms present in one
molecule of a compound.
• An empirical formula gives the simplest
whole-number ratio of elements in a
compound.
• The formula unit of an ionic compound is the
smallest electrically neutral unit within the
crystal of the compound.
NOMENCLATURE
I. Binary Ionic compounds
Binary means two different elements
Ionic means metal and nonmetal
Step 1
First give the name of the metal, followed by the
nonmetal name using the “ide” suffix.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to to
describe the charge of the metal. Except Ag,
Zn,and Al
Examples
NaCl
Al2O3
FeCl2
FeCl3
NOMENCLATURE
I. Binary Ionic compounds
Binary means two different elements
Ionic means metal and nonmetal
Step 1
First give the name of the metal, followed by the
nonmetal name using the “ide” suffix.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to to
describe the charge of the metal. Except Ag,
Zn,and Al
Examples
NaCl Sodium chloride
Al2O3
FeCl2
FeCl3
NOMENCLATURE
I. Binary Ionic compounds
Binary means two different elements
Ionic means metal and nonmetal
Step 1
First give the name of the metal, followed by the
nonmetal name using the “ide” suffix.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to to
describe the charge of the metal. Except Ag,
Zn,and Al
Examples
NaCl Sodium chloride
Al2O3 Aluminum oxide
FeCl2
FeCl3
NOMENCLATURE
I. Binary Ionic compounds
Binary means two different elements
Ionic means metal and nonmetal
Step 1
First give the name of the metal, followed by the
nonmetal name using the “ide” suffix.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to to
describe the charge of the metal. Except Ag,
Zn,and Al
Examples
NaCl Sodium chloride
Al2O3 Aluminum oxide
FeCl2 Iron(II) chloride
FeCl3
NOMENCLATURE
I. Binary Ionic compounds
Binary means two different elements
Ionic means metal and nonmetal
Step 1
First give the name of the metal, followed by the
nonmetal name using the “ide” suffix.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to to
describe the charge of the metal. Except Ag,
Zn,and Al
Examples
NaCl Sodium chloride
Al2O3 Aluminum oxide
FeCl2 Iron(II) chloride
FeCl3 iron(III) chloride
II. Nonbinary Ionic compounds
Nonbinary means more than two different elements
Step 1
First give the name of the metal, followed by the
memorized polyatomic ion name.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to describe
the charge of the metal. Except Ag, Zn, and Al.
Examples
NaOH
Fe(SO4)2
Fe(NO3)3
Zn(C2H3O2)2
Memorized Polyatomic Ion List
Formula
Name
Formula
Name
NH4+
Ammonium
O22-
Peroxide
C2H3O2-
Acetate
NO3-
Nitrate
CO32-
Carbonate
NO2-
Nitrite
HCO31-
Hydorgen carbonate
SO42-
Sulfate
ClO4-
Perchlorate
SO32-
Sulfite
ClO3-
Chlorate
PO43-
Phosphate
ClO2-
Chlorite
PO33-
Phosphite
ClO-
Hypochlorite
CrO42-
Chromate
CN-
Cyanide
Cr2O72-
Dichromate
MnO4-
Permanganate
C2O42-
Oxalate
OH-
Hydroxide
II. Nonbinary Ionic compounds
Nonbinary means more than two different elements
Step 1
First give the name of the metal, followed by the
memorized polyatomic ion name.
Step 2
CO
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to describe
the charge of the metal. Except Ag, Zn, and Al.
Examples
NaOH
Sodium hydroxide
Fe(SO4)2
Fe(NO3)3
Zn(C2H3O2)2
II. Nonbinary Ionic compounds
Nonbinary means more than two different elements
Step 1
First give the name of the metal, followed by the
memorized polyatomic ion name.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to describe
the charge of the metal. Except Ag, Zn, and Al.
Examples
NaOH
FeSO4
Sodium hydroxide
Fe(NO3)3
Iron(III) nitrate
Zn(C2H3O2)2
II. Nonbinary Ionic compounds
Nonbinary means more than two different elements
Step 1
First give the name of the metal, followed by the
memorized polyatomic ion name.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to describe
the charge of the metal. Except Ag, Zn, and Al.
Examples
NaOH
FeSO4
Sodium hydroxide
Iron(II) sulfate
Fe(NO3)3
Iron(III) nitrate
Zn(C2H3O2)2
II. Nonbinary Ionic compounds
Nonbinary means more than two different elements
Step 1
First give the name of the metal, followed by the
memorized polyatomic ion name.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to describe
the charge of the metal. Except Ag, Zn, and Al.
Examples
NaOH
FeSO4
Sodium hydroxide
Iron(II) sulfate
Fe(NO3)3
Iron(III) nitrate
Zn(C2H3O2)2
Iron(II) sulfate
III. Binary molecular Compounds
Molecular means nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide”
suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO
P2O5
CO2
CCl4
You will need to learn the Greek numerical prefixes (Table 4.6):
Number
1
2
3
Prefix
Mono-*
DiTri-
4
5
6
7
TetraPentaHexaHepta-
8
9
OctaNona-
10
Deca-
*Note 1
Compound
names never
start with mono
Note 2
When adding
a prefix two
vowls cannot
next to each
other
III. Binary Molecular Compounds
Molecular means nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide”
suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO Carbon monoxide
P2O5
CO2
CCl4
III. Binary Molecular Compounds
Molecular means nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide”
suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO Carbon monoxide CO2 Carbon dioxide
P2O5
CCl4
III. Binary Molecular Compounds
Molecular means nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide”
suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO Carbon monoxide
P2O5
CO2 Carbon dioxide
CCl4
II. Binary Ionic molecular
Molecular means combination of nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide”
suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO Carbon monoxide
CO2 Carbon dioxide
P2O5 Diphosphorus Pentoxide
CCl4
II. Binary Ionic molecular
Molecular means combination of nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide”
suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO Carbon monoxide
CO2 Carbon dioxide
P2O5 Diphosphorus Pentoxide
CCl4 Carbon tetrachloride
III. Nonbinary Molecular Compounds
Note: Do not use Latin prefixes
Step 1
Write down the memorized polyatomic ions present in
the compound.
Step 2
Look to see if any monatomic ions are present. If
so, then cations use the normal name. If it is an
anion, then its name comes last with the “ide” suffix.
Examples
NH4Cl
NH4OH
III. Nonbinary Molecular Compounds
Note: Do not use Latin prefixes
Step 1
Write down the memorized polyatomic ions present in
the compound.
Step 2
Look to see if any monatomic ions are present. If
so, then cations use the normal name. If it is an
anion, then its name comes last with the “ide” suffix.
Examples
NH4Cl
NH4OH
Ammonium chloride
III. Nonbinary Molecular Compounds
Note: Do not use Latin prefixes
Step 1
Write down the memorized polyatomic ions present in
the compound.
Step 2
Look to see if any monatomic ions are present. If
so, then cations use the normal name. If it is an
anion, then its name comes last with the “ide” suffix.
Examples
NH4Cl
Ammonium chloride
NH4OH
Ammonium hydroxide
Compounds that Start with Hydrogen
Case 1
If the anion ends in “ide” and it is aqueous,
then use the prefix hydro and suffix “ic acid”
Case 2
If the anion ends in “ate” then drop it and
add the suffix “ic acid”
Case 3
If the anion ends in “ite” then drop it
and add the suffix “ous acid”
Case 4
If the anion ends in” ide” and is a
gas, or liquid, then leave the name
and do not use Latin prefiex
Compounds that Start with Hydrogen
Examples
HCl (aq)
HNO3
HNO2
H2O (l)
HCl (g)
Anion Name
Chloride
Compound Name
Compounds that Start with Hydrogen
Examples
HCl (aq)
HNO3
HNO2
H2O (l)
HCl (g)
Anion Name
Compound Name
Chloride
Hydrochloric acid
Compounds that Start with Hydrogen
Examples
Anion Name
Compound Name
HCl (aq)
Chloride
Hydrochloric acid
HNO3
Nitrate
HNO2
H2O (l)
HCl (g)
Compounds that Start with Hydrogen
Examples
Anion Name
Compound Name
HCl (aq)
Chloride
Hydrochloric acid
HNO3
Nitrate
HNO2
H2O (l)
HCl (g)
Nitric acid
Compounds that Start with Hydrogen
Examples
Anion Name
Compound Name
HCl (aq)
Chloride
Hydrochloric acid
HNO3
Nitrate
HNO2
Nitrite
H2O (l)
HCl (g)
Nitric acid
Compounds that Start with Hydrogen
Examples
Anion Name
Compound Name
HCl (aq)
Chloride
Hydrochloric acid
HNO3
Nitrate
Nitric acid
HNO2
Nitrite
Nitrous acid
H2O (l)
HCl (g)
Compounds that Start with Hydrogen
Examples
Anion Name
Compound Name
HCl (aq)
Chloride
Hydrochloric acid
HNO3
Nitrate
Nitric acid
HNO2
Nitrite
Nitrous acid
H2O (l)
Oxide
HCl (g)
Compounds that Start with Hydrogen
Examples
Anion Name
Compound Name
HCl (aq)
Chloride
Hydrochloric acid
HNO3
Nitrate
Nitric acid
HNO2
Nitrite
Nitrous acid
H2O (l)
Oxide
Hydrogen oxide
HCl (g)
Compounds that Start with Hydrogen
Examples
Anion Name
Compound Name
HCl (aq)
Chloride
Hydrochloric acid
HNO3
Nitrate
Nitric acid
HNO2
Nitrite
Nitrous acid
H2O (l)
Oxide
Hydrogen oxide
HCl (g)
Chloride
Compounds that Start with Hydrogen
Examples
Anion Name
Compound Name
HCl (aq)
Chloride
Hydrochloric acid
HNO3
Nitrate
Nitric acid
HNO2
Nitrite
Nitrous acid
H2O (l)
Oxide
Hydrogen oxide
HCl (g)
Chloride
Hydrogen chloride
Oxy Anions & Related Acids
Anion
Anion Name
Acid
Acid Name
• ClO-
Hypochlorite
HClO
Hypochlorous acid
• ClO2-
Chlorite
HClO2
Chlorous acid
• ClO3-
Chlorate
HClO3
Chloric acid
• ClO4-
Perchlorate
HClO4
Perchloric acid
Practice
Write the names or chemical formulas
for the following compounds.
1.
2.
3.
4.
Cr(ClO4)3
Chromium(III) perchlorate
NH4NO3
Lithium bicarbonate
Calcium hypobromite
Practice
Write the name or chemical formula for
the following compounds.
1.
2.
3.
4.
NaCl
CrCl3
Zinc nitride
Copper(I) oxide
Practice
Write the names or chemical formulas
for the following compounds.
1.
2.
3.
4.
Cr(ClO4)3
NH4NO3
Lithium bicarbonate
Calcium hypobromite
Practice
Write the names or chemical formulas
for the following compounds.
1.
2.
3.
4.
Cr(ClO4)3
Chromium(III) perchlorate
NH4NO3
Lithium bicarbonate
Calcium hypobromite
Practice
Write the names or chemical formulas
for the following compounds.
1.
2.
3.
4.
Cr(ClO4)3
Chromium(III) perchlorate
NH4NO3
Ammonium nitrate
Lithium bicarbonate
Calcium hypobromite
Practice
Write the names or chemical formulas
for the following compounds.
1.
2.
3.
4.
Cr(ClO4)3
Chromium(III) perchlorate
NH4NO3
Ammonium nitrate
Lithium bicarbonate LiHCO3
Calcium hypobromite
Practice
Write the names or chemical formulas
for the following compounds.
1.
2.
3.
4.
Cr(ClO4)3
Chromium(III) perchlorate
NH4NO3
Ammonium nitrate
Lithium bicarbonate LiHCO3
Calcium hypobromite Ca(BrO)2
The End Ch #2
Atoms and Elements