Chapter 2: The
Chemistry of
Biology
The Composition of the Universe
A. Element: a pure substance that cannot be
broken down chemically into other kinds of
matter.
1. Ex: Oxygen, Carbon, Hydrogen, Nitrogen,
Phosphorus
http://vimeo.com/4433312
http://www.youtube.com/watch?v=d0zION8xjbM&safety_mode=true&persist
_safety_mode=1
The Composition of the Universe
B. Atom: simplest part of an element
C. Subatomic Particles: Parts of an atom
1. Protons: positively (+) charged particles
a. Found in the nucleus of an atom
2. Neutrons: neutral particles
a. Found in the nucleus of an atom
http://www.youtube.com/watch?v=xqNSQ3OQMGI
The Composition of the Universe
3. Electrons: negatively charged particles
a. Found moving around the nucleus in
energy levels
b. Valence electrons – electrons in the last
shell or energy level of an atom
** Hint: ** The number of valence electrons
for an atom, is determined by the column
(group) number it falls under on the Periodic
Table of Elements. For example, an atom in
the 3rd column, have 3 valence electrons.
http://www.youtube.com/watch?v=xqNSQ3OQMGI
The Composition of the Universe
The
Electron Energy Levels
Bohr Model of Carbon:
The Composition of the Universe
Lewis Dot Structure:
http://www.youtube.com/watch?v=xqNSQ3OQMGI
The Composition of the Universe
D. How do you determine the number of protons?
1. Equal to the atomic number
E. How do you determine the number of
electrons?
1. Equal to the # of protons (atomic number)
in a stable atom
F. How do you determine the number of neutrons?
1. Equal to the Atomic Mass (rounded) – Atomic #
The Composition of the Universe
The
Electron Energy Levels
Bohr Model of Carbon:
Bonding
A. All atoms “want” to be stable; if they do not have
8 valence electrons in their outer most shell, then
they tend to undergo reactions to find stability
1. BONDS are then formed!
Bonding
Type of
Bond
Ionic
Occurs
or Found
Between
?
Metals
and
Nonmetals
How is the
bond
formed?
Electrons are
transferred
between
atoms
Additional Info
Ion: positive & negatively
charged atoms formed
(Na+, Cl-)
Bonding
 Is
it easier for Potassium to gain or lose
electrons to have a stable outermost ring of
electrons?
Bonding
 What
about Chlorine?
The Composition of the Universe
 Ionic
Bonding Results
The Composition of the Universe
Bonding
Type of
Bond
Covalent
Occurs or
Found
Between?
How is the bond
formed?
Electrons are
2 or more
Non-metals shared between
atoms
Additional Info
Can be polar or nonpolar bonds
depending on
electron sharing
Bonding
Type of
Bond
Van der
waals
forces
Occurs or
Found
Between?
How is the bond
formed?
Oppositely
charged areas of
molecules are
(intermolecular) attracted to each
other
Between
molecules
Additional Info
Very weak bonds;
allows geckos to
walk upside down;
found between
water molecules
+
-
ATTRACTION OF
DIFFERENT CHARGES
BETWEEN MOLECULES
Bonding
 Ex:
Gecko Foot – has half a
million hair like projections
that are divided into fibers
 Forces
form between the
hairs on the feet and
surface allowing the
gecko to balance gravity
http://www.youtube.com/watch?v=OoYeIsSkafI
Building More Complex Substances
B. Building More Complex Substances
1. Compound: substance formed by the
chemical combination of atoms from two or more
elements
a. Ex: H2O (water), C6H12O6 (glucose), CO2 (carbon
dioxide)
 The
properties of the compound are different than
those of the elements that create it!
Building More Complex Substances
B. Molecule: the simplest form of a
compound; when two or more atoms join
1. Ex: O2 (oxygen gas), H2O (water)
 *All
compounds are molecules, but not all
molecules are compounds**
Mixing It Up…Solutions!
A. Solution: a mixture in which
one or more substances are
uniformly distributed in another
substance.
1. Two major components
a. Solute: substance
dissolved into the solution
b. Solvent: substance in
which the solute is dissolved
 Ex:
WATER IS THE UNIVERSAL
SOLVENT
Mixing It Up…Solutions!
B. How do we analyze the strength of a solution?
Concentration (amount of solute dissolved in solution)
10g
100mL
20g
100mL
30g
40g
50g
100mL
100mL
100mL
pH Scale
A. pH Scale: measures the concentration of
hydrogen (H+) ions and hydroxide ions (OH-) in
solution
 Range of the Scale: 0-14
pH
 Acid:
 Range:
0-7
 H+
Ions: [High]
 OH – Ions: [Low]
 Ex:
HCl (stomach acid), milk
pH
 Base:
 Range:
7-14
 H+
ions: [Low]
 OH- ions: [High]
 Ex:
Blood, Ammonia, Sea
Water
pH
 Neutral:
 Range:
7
 H+
ions: [Equal]
 OH- ions: [Equal]
 Ex:


WATER!
What are the strong acids?
What are the strongest bases?
The Chemistry of Water
A. COVALENT bonds: join
hydrogen and oxygen that make
up water
1. Electrons are not shared
EQUALLY!
a. Oxygen has 8
electrons
b. Hydrogen only has 1
electron
 The
oxygen atom pulls
the shared electrons
towards its own nucleus
and away from the
hydrogen.
The Chemistry of Water
B. Polarity: the distribution of
charges in atoms joined by a bond
1. Polar compound: a molecule
with an uneven pattern of
charge or unequal sharing of
electrons
a. Ex: Water, Sugars,
Proteins, DNA (good at
dissolving things!)
2. Non-polar compound: a
molecule with an even pattern of
charge or equal sharing of
electrons
a. Ex: Oxygen gas, fats,
waxes
+
+
-
Polarity of Water
C. Polarity of WATER
1. Causes water molecules to attract to
each other or be “sticky” and form van der
waals forces between them
a. Hydrogen Bond: attraction holding
two+ water molecules together
Positive (H+) region of one water
molecule is attracted to the negative
(O-) region of another
These are weak bonds; they can be
broken easily!
Why is hydrogen bonding
important to life and biology?
A. Creates cohesion of particles
1. Attractive forces between particles of the
same type
a. Ex: Water “sticks” allowing striders to move
across; Floating a paperclip on water
Polarity of Water
 Surface
Tension: created by cohesion; a
force existing on the surface of a liquid,
preventing the layer from being broken
http://www.youtube.com/watch?v=8O8PuMkiimg&safety_mode=tru
e&persist_safety_mode=1
Why is hydrogen bonding
important to life and biology?
B. Creates adhesion of particles
1. Attractive forces between different/unlike substances
a. Ex: meniscus on a test tube
Why is hydrogen bonding
important to life and biology?
C. Capillary Action: water molecules move upward
through narrow tubes against the force of gravity
because of cohesion and adhesion
1. Ex: flower, redwood tree
Why is hydrogen bonding
important to life and biology?
D. High Specific Heat Capacity & Heat of
Vaporization:
1. Water must gain or lose large amounts of
energy (heat) to break the hydrogen bonds for
any temperature change or evaporation to
occur.
a. Why is this important?
Helps organisms maintain homeostasis
 Helps moderate climate/ocean water temperature

Why is hydrogen bonding
important to life and biology?
E. Water EXPANDS becomes LESS dense when
it freezes!
1. Why is this significant?
a. Ice floats preventing the water from
freezing solid and insulates the lower
layers, allowing life to survive underneath it
Why is hydrogen bonding
important to life and biology?
F. Water is the universal solvent.
1. Water dissolves more solutes than any
other liquid.
 Penny
Lab Video
 http://www.youtube.com/watch?v=8O8P
uMkiimg&safety_mode=true&persist_safet
y_mode=1