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Chapter 2
The Components of Matter
He
C60
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1
Classification of Matter
by composition
Matter is anything that has mass and volume (i.e.,
occupies space)
physically separable
chemically combining
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2.1 Elements, Compounds, &
Mixtures: An Atomic Overview
Pure Substance: A single chemical; one kind of
matter, uniform in its chemical composition and
properties. Examples: Oxygen gas, copper, sugar,
water, etc…
Mixture: A blend of two or more pure
substances in any ratio, each retaining its identity;
physical and chemical properties vary as the
relative amounts of different parts change.
Dissolving sugar in water creates a mixture.
Can be separated into pure substances by
physical changes. Evaporation and condensation
can separate water from sugar.
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A pure substance is classified as matter with a
specific composition.
An element when composed of one type
of atom, and canNOT be broken down
chemically into simpler substances.
Hydrogen and oxygen are examples of
elements.
A compound when composed of two or
more types of elements combined in a
definite ratio, and can be decomposed by
a chemical change into two or more other
pure substances.
Water is a compound composed of two
parts hydrogen and one part oxygen.
Water can be broken down into hydrogen
and oxygen by passing an electric current
through it.
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Elements and Atoms
Elements are
Atoms are
- Pure substances that
cannot be separated
into simpler
substances by
ordinary laboratory
processes.
- The building blocks
of matter.
- smallest identifiable
units of elements.
- What do atoms look
like?
Definitely small! If
100,000,000 copper
atoms were placed
side by side, they
would form a line 1
cm long.
Element Symbol: S,
Cu, Fe,…
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Compounds & Molecules
 COMPOUNDS are a
combination of 2 or more
elements in definite ratios.
 The character of each
element is lost when
forming a compound.
MOLECULES are the
smallest unit of a
compound that retains
the characteristics of the
compound.
 CHEMICAL FORMULAS
indicate the elements
present in the compound
and the relative number of
atoms of each.
Ethanol, C2H6O
Buckyball, C60
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2.9 Mixtures
Homogeneous: A sample that has
a uniform appearance and
composition throughout. Solution
is
A homogeneous mixture.
Examples: Coffee, air, brass
Heterogeneous: Different phases,
usually visible The composition is not
uniform, it varies from one part of the
mixture to another.
.
Examples: Carbonated beverages,
salad dressings
2.2
Law of Conservation of Mass
- When atoms combine into a compound, the
mass of the compound is the sum of these
atomic masses.
- In a chemical reaction, mass is not gained or
lost. the total mass of the products always
equals to the total mass of the reacting
substances.
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Law of Definite Proportions
All samples of the same compound contain the
same proportions by mass of the component
elements in a simple ratio of whole numbers.
2.3 Dalton’s Atomic Theory (1808)
In Greek, ‘a’ means ‘no’; ‘tom’ means ‘cut’; ‘atom’ is the smallest, indivisible piece of matter
1) Atoms are the smallest identifiable units of elements.
2) Atoms of a given element are identical to one another,
but different from atoms of any other element.
3) Atoms are rearranged in chemical reactions, but neither
the number nor the types of atoms is changed in
reaction
4) Compounds are formed by atoms coming together to
form molecules in which the number of each type of
atom is constant.

What do atoms look like?
 Definitely small! If 100,000,000 copper atoms were placed
side by side, they would form a line 1 cm long.
 Scanning tunneling microscope helps us to see them.
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2.5 The Nuclear Model
of the Atom
-1 0
10
m
Nu cleus (protons an d neu trons)
Space occupied by electrons
Proton
Neu tron
-1 5
10
m
The diameter of the nucleus
is about 100,000 times
smaller than that of the
whole atom. The correct
scale would be comparable
to a penny (the nucleus) in
the center of the baseball
field (the atom)
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Introduction to General, Organic, and Biochemistry, 7th Ed. By Bettelheim, Brown, and March, Thomson Publishing
Subatomic Particles
Atom contains subatomic
particles.
 Electrons have a negative (-)
charge.
 Protons have a positive (+)
charge.
 Neutrons are neutral.
 Like charges repel and unlike
charges attract.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
12
Particles in the Atom
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Atomic Number (Z)




Is specific for each element.
Is the same for all atoms of an element.
Is equal to the number of protons in an atom.
Appears above the symbol of an element.
Atomic number
Symbol
11
Na
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Mass Number (A)
 Represents the total number of particles in the
nucleus.
 Mass number = # of protons + # of neutrons
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Atomic Symbol
 Represents a particular atom of
an element by showing the element symbol
 Gives the mass number in the upper left corner
and the atomic number in the lower left corner of
the element symbol.
 An isotope is identified by its mass number
Example: An atom of sodium with atomic
number 11 and a mass number 23 has the
following atomic symbols:
23 Na , 23Na, Na-23
mass number
atomic number 11
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Learning Check
Write the isotope symbols for atoms with the following subatomic
particles:
A. 8 p+, 8n, 8e___________
B. 17p+, 20n, 17e- ___________
C. 47p+, 60 n, 47 e- ___________
1. Which of the following pairs are isotopes of the same element?
2. In which of the following pairs do both atoms have
8 neutrons?
A. 15X 15X
8
B.
C.
7
12X 14X
6
6
15X
16X
7
8
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Isotopes
Isotopes are atoms of the
same element that have the
same number of protons,
but different numbers of
neutrons.
24Mg
12
25Mg 26Mg
12
12
Name of an Isotope =
Elemental name–Mass number
Carbon-12 = A carbon atom with 6 protons
and 6 neutrons
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Atomic Masses of the Elements
How big is an atom?




Very tiny!!
A hydrogen atom has mass 1.67 x 10-24 g
A sodium atom has mass 3.817 x 10-23 g
We define a new unit:
atomic mass unit (amu or u) = 1/12 the mass of a
carbon-12 atom
1 amu = 1.6603 x 10-24 g
So, what is the mass of a hydrogen atom, a sodium
atom in amu?
11
 A hydrogen atom has mass 1.008 amu
 A sodium atom has mass 22.99 amu
Na
22.99
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Atomic Mass (of an element):
The average mass of all atoms of an
element as they occur in nature.
Chlorine has two natural isotopes:
75.78% is chlorine-35 at 34.968852721 amu
24.22% is chlorine-37 at 36.96590262 amu
What is the atomic mass of chlorine?
0.7578 x 34.968852721 amu =
0.2422 x 36.96590262 amu =
26.50 amu
8.953 amu
35.45 amu
Learning Check
 In nature 10B atom with a mass of 10.01294 u is
19.9% abundant, and 11B with a mass of 11.00931
u is 80.1%. Calculate atomic mass of B.
 The relative atomic mass of silver is 107.9 amu. If
silver is composed of only Ag-107 and Ag-109,
which isotope is most abundant?
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2.6 Elements: A First Look
at the Periodic Table
 How do we keep track
of all these elements?
 Dmitri Mendeleev –
Russian chemist
(1834-1907)
 He listed the
elements and their
properties on
individual cards, and
organized them.
 Great simplification
in chemistry!
Tro, Nivaldo J., Chemistry in Focus: A Molecular View of
our World, 3rd Ed., Thomson Brooks/Cole, 2007.
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The Periodic Table
 First, Mendeleev
arranged the elements
in order of increasing
atomic mass
He examined chemical
properties and found a
trend!
Mendeleev then arranged elements
with recurring sets of properties in
the same column (vertical row) and
with increasing atomic number in
periods (horizontal rows)
He found he had 8 columns of elements
that had similar chemical properties.
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Organization of the Periodic Table
 Groups contain elements with similar
properties in vertical columns.
 Periods are horizontal rows of elements
in the order of increasing atomic number.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
24
Classifying the Elements
Copyright © 2007 by Pearson Education,25
Inc.
Publishing as Benjamin Cummings
Properties of Metals, Nonmetals, and
Metalloids
Metals
 Are shiny and ductile.
 Are good conductors of heat and electricity.
Nonmetals
 Are dull, brittle
 Are poor conductors of heat and electricity.
 Are good insulators.
Metalloids
 Are better conductors than nonmetals, but
not as good as metals.
 Are used as semiconductors and
insulators.
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Group Names
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Learning Check
Identify the element described by the following:
A. Group 7A(17), Period 4
1) Br
2) Cl
3) Mn
B. Group 2A(2), Period 3
1) beryllium
2) magnesium
3) boron
C. Group 5A(15), Period 2
1) phosphorus
2) arsenic
3) nitrogen
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ELEMENTS THAT EXIST AS
POLYATOMIC or DIATOMIC MOLECULES
White P4 and polymeric
red phosphorus
MEMORIZE
THEM!
S8 sulfur
molecules
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2.7 & 2.8 Compounds:
Formulas, Names, & Masses
Why do compounds form?
- Except for the noble gases, elements usually
form compounds with other elements to gain
stability.
Two major types of compounds:
1) ionic (metal + non-metal): loss/gain
2) molecular (non-metal + non-metal):
sharing equally or unequally
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The Formation of Ionic Compounds
 IONS are atoms or groups of atoms with a
positive or negative charge.
 Taking away an electron from an atom gives
a CATION
with a positive charge
 Adding an electron to an atom gives an
ANION with a negative charge.
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Forming Cations & Anions
A CATION forms
when an atom
loses one or more
electrons.
Mg -->
Mg2+
+ 2 e-
An ANION forms
when an atom
gains one or more
electrons
F + e- --> F32
Electrostatic Forces
COULOMB’S LAW
As ion charge increases, the attractive force increases.
As the distance between ions increases, the attractive force
decreases.
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Properties of
IONIC COMPOUNDS
 Ionic compounds are composed of
repeating positive and negative ions in
large arrays (called a lattice).
 Formula unit of an ionic compound is
the simplest whole number ratio.
NaCl, salt
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PREDICTING ION CHARGES
In general, for MONOATOMIC IONS of Main Group elements
 metals lose electrons ---> cations
ion charge = group #
Mg --> Mg2+ + 2 e-
 nonmetals gain electrons ---> anions
ion charge = group # - 8
F + e- --> F-
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Predicting Charges on Monatomic Ions
For monoatomic ions of Transition Elements:
Common ion charge is 2+ or 3+
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Names of METAL Ions
Main Groups:
Na+
sodium ion
Mg2+
magnesium ion
Al3+
aluminum ion
Transition metals
Fe2+
iron(II) ion
Fe3+
iron(III) ion
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Names of NONMETAL Ions
Group 4A
Group 5A
Group 6A
Group 7A
C4-,carbide N3-, nitride O2-, oxide F-, fluoride
Name derived by
adding -ide to
stem
S2-, sulfide Cl-, chloride
Br-, bromide
I-, iodide
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Polyatomic Ion
 Is a group of atoms bonded
together.
 Has an overall ionic charge that
belongs to the whole group.
 In naming, simply use the name
of the polyatomic ion. No
ending change is needed.
 The most common polyatomic
cation is NH4+.
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Note: many O
containing anions
have names ending in
–ate (or -ite).
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Acids Names and Their Anions
Naming Ionic Compounds
1. Identify the cation and anion.
2. The cation is always named first.
3. The base name of the anion is written next,
but the ending of –ide is placed on the end.
4. DO NOT use numeric prefixes in naming
ionic compounds! So you really need to be
sure you are naming an ionic compound.
5. Some transition metals require that you place
a Roman numeral after the name to indicate
the charge.
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Naming Compounds with Polyatomic Ions
 The positive ion is named first followed
by the name of the polyatomic ion.
NaNO3
sodium nitrate
K2SO4
potassium sulfate
Fe(HCO3)3
iron(III) bicarbonate
or iron(III) hydrogen carbonate
(NH4)3PO4
ammonium phosphate
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Naming Ionic Compounds with
Variable Charge Metals
Transition metals that form two different
ions use a Roman numeral after the
name of the metal ion to indicate the
charge.
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Writing Formulas from the Name
Write a formula for potassium sulfide.
STEP 1 Identify the cation and anion.
potassium = K+
sulfide
= S2−
STEP 2 Balance the charges.
K+
S2−
K+
2(1+) + 1(2-) = 0
STEP 3 Write the cation first. Add subscripts as needed
2K+ and 1S2− = K2S1 = K2S
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Learning Check
The correct formula for each of the following is:
A. Copper (I) nitride
E. Lead (IV) oxide
B. calcium nitrate
F. iron(II) hydroxide
C. aluminum carbonate
G. copper(II) bromide
D. lithium phosphate
Name the following compounds:
A. Ca3(PO4)2
B. FeBr3
D. Zn(NO2)2
E. NaHCO3
C. Al2S3
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Naming and Writing Formulas for
Binary Covalent Compounds
A. The first word is the name of the first element in the
compound.

A prefix is used to indicate the number
B. The second word is the name of the second element in
the compound. Its ending should be changed to –IDE.

A prefix is also used to indicate the number
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Names of Molecular Compounds
Prefixes are used in the names of molecular
compounds, because two nonmetals can
form two or more different compounds.
 Examples of compounds of N and O:
NO
nitrogen oxide
NO2
nitrogen dioxide
N2O
dinitrogen oxide
N2O4
dinitrogen tetroxide
N2O5
dinitrogen pentoxide
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Guide to Writing Formulas
STEP 1 Write the symbols in the order of
the elements in the name.
STEP 2
Write any prefixes as subscripts.
Example: Write the formula for carbon
disulfide.
STEP 1
Elements are C and S
STEP 2
No prefix for carbon means 1 C
Prefix di = 2
Formula: CS2
49
Learning Check
Name of the following molecules.
CCl4
BCl3
SF6
Write the correct formula for each of the
following:
A. phosphorus pentachloride
B. dinitrogen trioxide
C. sulfur hexafluoride
50
Molecular (Formula) Masses
from Chemical Formulas
For a compound, the formula mass is the sum of
atomic masses of the elements in the formula.


Element
Number of
Moles
Atomic Mass
Total Mass in
K3PO4
K
3
39.10 amu
117.3 amu
P
1
31.00 amu
31.00 amu
O
4
16.00 amu
64.00 amu
K3PO4
51
212.3 amu
Ball-and-stick model:
Symbolizes atoms as balls and the
electrons that connect those atoms
as sticks
Space-filling model:
Shows the outer boundaries of the
particle in three-dimensional space
Representing Molecules
with Formula & Models
Chemical formula
and
Lewis diagram
Hydrate: A
solid compound that
includes water
molecules in its
crystal structure
Vocabulary of Hydrates
Water of Crystallization
or Water of Hydration
Water molecules that are part of the
crystal structure in a hydrate
Anhydrous Compound
An ionic compound that is without water or
from which water has been removed
Formulas of Hydrated Compounds
Formula of ionic compound, followed by the
number of water molecules that crystallize
with each formula unit of the anhydrous
compound, separated by a dot
CaSO4 • 2 H2O
There are two water molecules
for each formula unit of calcium sulfate
Naming Hydrates
Use the prefixes used in naming binary
molecular compounds to indicate the
number of water molecules associated
with each formula unit of the anhydrous compound
What is the name of Al2O3 • 3 H2O?
Aluminum oxide trihydrate
What is the formula of
iron(III) sulfate nonahydrate?
Fe2(SO4)3 • 9 H2O
57
Fig. 7-2b, p. 185