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Chapter 2
Matter
and
Energy
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Matter and Energy
 Matter—anything that occupies space and has
mass
 Energy—the ability to do work
(for biologists, it includes-)
 Chemical energy
 Mechanical energy
 Heat
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All matter is composed of atoms
 About 120 elements, 91 occur naturally
 96% of the body is made from four elements
 Carbon (C)
 Hydrogen (H)
 Oxygen (O)
 Nitrogen (N)
CHON
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All matter is composed of atoms
CHON
 Other elements in the body include:
Ca, P, K, S, Na, Cl, Mg, I, Fe
 Trace elements include: Cr, Cu, Co, F, Mn and
others
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Atomic Structure – Subatomic particles
Name
Symbol
Mass
Charge
Location
Proton
Neutron
Electron
Figure 2.1
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Atomic Structure – Subatomic particles
 Name
Symbol
Mass
Charge
 Proton
p
1 amu
+1
 Neutron
n
1 amu
0
 Electron
e-
0 amu
-1
Location
in nucleus
in nucleus
around
nucleus, in
electron cloud
Figure 2.1
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Atomic Structure
Figure 2.1
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Atomic Structure of Smallest Atoms
Electrons have different
energy levels. Only the
outer level affects an atom’s
chemical properties!
Figure 2.2
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Identifying Elements
 Atomic number —equal to the number of
protons
 Atomic mass number —sum of the
protons and neutrons
Atomic Number =
number of protons
Name
19
39.0983
K
Average atomic
mass, in amu/atom
Potassium
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Symbol
Identifying Elements
Name
Symbol
Atomic
Number
Atomic
Mass
Number
#p
#n
(most
likely)
Sulfur
K
20
17
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# e-
Identifying Elements
Name
Symbol
Atomic
Number
Atomic
Mass
Number
#p
#n
# e-
(most
likely)
Sulfur
S
16
32
16 16
16
Potassium
K
19
39
19 20
19
Calcium
Ca
20
40
20 20
20
Chlorine
Cl
17
35
17 18
17
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Isotopes and Mass Number
 Isotopes
 Have the same number of protons
 Vary in number of neutrons
Figure 2.3
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Isotopes and Mass Number
 Chlorine has two common isotopes,
Cl-35 and Cl-37
Figure 2.3
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Isotopes and Mass Number
 Chlorine has two common isotopes,
Cl-35 and Cl-37
 How many neutrons in each?
Figure 2.3
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Isotopes and Mass Number
 Chlorine has two common isotopes,
Cl-35 and Cl-37
 How many neutrons in each?
 How many protons in each?
Figure 2.3
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Isotopes and Mass Number
 Chlorine has two common isotopes,
Cl-35 and Cl-37
 How many neutrons in each?
 How many protons in each?
 Which one is more common?
Figure 2.3
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Isotopes and Mass Number
 Chlorine has two common isotopes,
Cl-35 and Cl-37
 How many neutrons in each?
18 and 20
 How many protons in each?
17
 Which one is more common?
Cl-35
Figure 2.3
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Isotopes and Average Atomic Mass
 Average atomic mass
 Usually closest to mass number of most
abundant isotope
 Average atomic mass reflects natural isotope
variation
 Take the average atomic mass and round to
the nearest whole number for the mass
number of the most common isotope
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Isotopes and Average Atomic Mass
 The periodic table is arranged by atomic number.
 The average atomic mass usually increases with
atomic number.
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Isotopes and Average Atomic Mass
 The periodic table is arranged by atomic number.
 The average atomic mass usually increases with
atomic number.
 Find 3 exceptions.
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Isotopes and Average Atomic Mass
 The periodic table is arranged by atomic number.
 The average atomic mass usually increases with
atomic number.
 Find 3 exceptions.
 Why does this (rarely) occur?
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Isotopes and Average Atomic Mass
 The periodic table is arranged by atomic number.
 The average atomic mass usually increases with
atomic number.
 Find 3 exceptions.
 Why does this (rarely) occur?
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Radioactivity—process of spontaneous atomic decay
 Radioisotopes are radioactive
 Typically an unusually heavy isotope
 Tend to be unstable
 Decompose to more stable isotope
 Used in medical diagnosis and treatment
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Compounds
 Elements combine to form compounds.
Figure 2.4
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Chemical Reactions
 Atoms are joined by chemical bonds (ionic or
covalent)
 A chemical reaction forms and/or breaks chemical
bonds
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Electrons and Bonding
 Electrons occupy energy levels
 Each level has distinct properties
 The number of electrons has an upper limit
 Levels closest to the nucleus fill first
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Electrons and Bonding
 Bonding involves electrons in the outer level
(the valence shell)
 The ROW on the periodic chart indicates the
valence level
 Full valence shells do not form bonds
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Bonding leads to stability
 Atoms are stable when the outermost level is
complete
 How to fill the energy levels
 Level 1: maximum of 2 electrons
 Level 2: maximum of 8 electrons
 Level 3: maximum of 18 electrons
 The valence shell can hold a maximum of 8
electrons
 The COLUMN on the periodic chart indicates the
number of valence electrons in an atom
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 Atoms will gain, lose, or share
electrons to complete their valence
shells and reach a stable state
 Octet Rule – the Rule of eights
 Atoms are considered stable when their
valence shell has 8 electrons
 (Except for level 1, Hydrogen: use the duet
rule)
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Inert Elements
Figure 2.5a
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Reactive Elements
 Valence shells are not full and are unstable
 Tend to gain, lose, or share electrons
 These elements form chemical bonds!
Figure 2.5b
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Chemical Bonds
 Ionic bonds
 Form when electrons are transferred from one
atom to another
 Ions
 Charged particles—protons don’t equal electrons
 Cations are positive (have lost e-)
 Anions are negative (have gained e-)
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Chemical Bonds
 Ionic bonds
 Form when electrons are transferred from one
atom to another
 Ions
 Charged particles—protons don’t equal electrons
 Cations are positive (have lost e-)
 Anions are negative (have gained e-)
Metals lose
electrons
Nonmetals gain (or
share) electrons
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Identifying
Name
Ions
Symbol
Atomic
Number
Atomic
Mass
Number
#p
#n
(most
likely)
Iodide
ion
Na+
9
12
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# e-
Identifying Ions
Name
Atomic
Number
Atomic
Mass
Number
I-
53
127
53 74
54
Sodium
ion
Na+
11
23
11 12
10
Fluoride
F-
9
19
9
10
10
Mg+2
12
24
12 12
10
Iodide
Symbol
#p
#n
# e-
(most
likely)
ion
ion
Magnesium
ion
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Ionic Bonds
Na
Cl
Sodium atom (Na)
(11p+; 12n0; 11e–)
Chlorine atom (Cl)
(17p+; 18n0; 17e–)
Figure 2.6, step 1
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Ionic Bonds
Na
Cl
Sodium atom (Na)
(11p+; 12n0; 11e–)
Chlorine atom (Cl)
(17p+; 18n0; 17e–)
Figure 2.6, step 2
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Ionic Bonds
Na
Cl
Sodium atom (Na)
(11p+; 12n0; 11e–)
Chlorine atom (Cl)
(17p+; 18n0; 17e–)
+
–
Na
Cl
Sodium ion (Na+)
Chloride ion (Cl–)
Sodium chloride (NaCl)
Figure 2.6, step 3
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Chemical Bonds
 Covalent bonds
 Atoms become stable through shared
electrons
 Single covalent bonds share one pair of
electrons
 Double covalent bonds share two pairs of
electrons
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Examples of Covalent Bonds
Figure 2.7a
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Examples of Covalent Bonds
Figure 2.7b
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Examples of Covalent Bonds
Figure 2.7c
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Valence Rules
In general:
Carbon makes 4 bonds
Hydrogen makes 1 bond
Oxygen makes 2 bonds
Nitrogen makes 3 bonds
Figure 2.7c
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Polarity —the most important chemical property
Figure 2.8
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Polarity —the most important chemical property
 Some molecules are
non-polar
 Some are polar
 Have a positive and
negative side
Figure 2.8
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What bonds are polar?
 Look for:
O-H
C-O
or
N-H…
…bonds in a molecule
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Attraction between molecules
 Polarity provides attraction between molecules
 Weak chemical bonds
 Hydrogen bonds-- Hydrogen is attracted to the
negative portion of polar molecule
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Hydrogen Bonds
Causes surface tension in water
Figure 2.9
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Chemical Reactions
 Reactants form products
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Chemical Reactions
 Reactants form products
A + B  C + D
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Chemical Reactions
 Reactants form products
A + B  C + D
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Chemical Reactions
 Reactants form products
A + B  C + D
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Patterns of Chemical Reactions
 Synthesis reaction (A + BAB)
 Atoms or molecules combine
 Energy is absorbed
 Decomposition reaction (ABA + B)
 Molecule is broken down
 Chemical energy is released
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Synthesis and Decomposition Reactions
Figure 2.10a
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Synthesis and Decomposition Reactions
Figure 2.10a
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Synthesis and Decomposition Reactions
Figure 2.10b
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Synthesis and Decomposition Reactions
Figure 2.10b
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Patterns of Chemical Reactions
 Exchange reaction (AB + CAC + B)
 Involves both synthesis and decomposition
reactions
 Switch is made between molecule parts and
different molecules are made
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Patterns of Chemical Reactions
Figure 2.10c
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Patterns of Chemical Reactions
Figure 2.10c
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