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BIOLOGIC
CHEMISTRY
Chapter 2 – Part 1
The Chemistry of Life
CP Biology
Paul VI Catholic High School
BIOLOGIC CHEMISTRY
NATURE OF MATTER:
ATOMS: “Basic unit of matter”
An atom is the smallest portion of a substance that still
retains the unique properties of that substance.
• PROTONS: Positive charge (1.009 DALTONS)
• NEUTRONS: No Charge (1.007 DALTONS)
• ELECTRONS: Negative charge (1/1840 DALTONS)
1 DALTON = 1.66054X10-24 kilograms
(1/12 the mass of Carbon)
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NUCLEUS:
• CENTER OF ATOM
• CONTAINS PROTONS AND NEUTRONS
ORBITALS:
• CONTAIN ELECTRONS
In a neutral atom, the number of protons equals
the number of electrons
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ELECTRON CONFIGURATION:
ENERGY LEVELS CONTAIN:
2, 8, 18, 32 electrons
ENERGY SUBLEVELS:
s level: 2 electrons
p level: 6 electrons
d level: 10 electrons
f level: 14 electrons
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Periodic chart (including Bohr models)
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• Periodic means repeating in a pattern
The Periodic Table of Elements
…is the arrangement of elements according to
repeating changes in properties .
• The boxes for the elements are arranged in
order of their atomic numbers.
• Vertical columns are groups or families.
• Horizontal rows are called periods.
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ELEMENT:
Atomic Number = protons
Atomic Mass = protons + neutrons
ISOTOPES:
Vary in number neutrons
Same Chemical Properties
Some Radioactive
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Biology, Seventh Edition
CHAPTER 2 Atoms and Molecules: The Chemical Basis of Life
Carbon Isotopes
Copyright © 2005 Brooks/Cole — Thomson Learning
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RADIOACTIVE DECAY:
α waves
β waves
γ waves
CARBON DATING:
“Half-Life” 5600 years
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CHEMICAL COMPOUNDS:
Substances formed by the combination
of two or more different elements in a
fixed ratio. They are “pure” substances.
MOLECULE:
Smallest unit of covalently bonded
compound.
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A chemical formula uses the symbols
for the elements in the compound.
Na + Cl → NaCl
Some formulas include subscripts to
show ratios of more than one atom.
2 H + 1 O → H20
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CHEMICAL FORMULA: Shorthand expression
describing chemical composition
SIMPLEST FORMULA
(Empirical Formula)
CaN2O6
MOLECULAR FORMULA
Ca(NO3)2
STRUCTURAL FORMULA
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CHEMICAL BONDS:
Bond energy is the energy necessary to break a chemical
bond.
• COVALENT BOND
• holds molecule together by sharing electrons
• IONIC BOND
• holds molecule together by transfer of electrons
• VAN DER WAALS FORCES
• temporary dipole attraction between molecules
• Results in higher boiling points
• HYDROGEN BONDS
• Attraction between molecules with partially positive
and partially negative areas
BIOLOGIC CHEMISTRY
Biology, Seventh Edition
CHAPTER 2 Atoms and Molecules: The Chemical Basis of Life
Covalent bonds
Copyright © 2005 Brooks/Cole — Thomson Learning
BIOLOGIC CHEMISTRY
Biology, Seventh Edition
CHAPTER 2 Atoms and Molecules: The Chemical Basis of Life
Ionic bonding
Copyright © 2005 Brooks/Cole — Thomson Learning
Hydrogen
Bonding
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• Hydrogen bondspartially positive
charged “H”end of a
molecule is attracted
to partially negative
charged end of
another molecule
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CHEMISTRY OF WATER:
ATOMIC STRUCTURE:
10 Protons
10 Electrons
Covalent Bond
Polar Structure
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PROPERTIES OF WATER:
1. COHESION:
Attraction between molecules of the same substance.
2. ADHESION: Attraction between different substances.
3. HIGH SPECIFIC HEAT:
1Cal./gm/oC
4. HIGH HEAT OF VAPORIZATION:
(Heat energy required to change 1 gm. liquid water to gas.)
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SOLUTION: Homogeneous (uniform) mixture of a
liquid.
solvent- dissolving agent
solute- substance that is dissolved
aqueous solution- solution with water as solvent
MIXTURE: Substance composed of two or more
elements or compounds that are together BUT are
not chemically combined.
SUSPENSION: Composed of nonpolar molecules in
water. Water acts to exclude them.
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COLLOIDS: Heterogeneous mixtures containing
particles intermediate in size between suspensions
and solutions.
TYNDALL EFFECT – light scattering effect in colloids
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ACID / BASE / pH
pH: (“pouvoir hydrogene”)
Calculated from the spontaneous dissociation of water
Negative logarithm of the [H+]
Each change in a pH unit is a tenfold change in
concentration
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ACIDS:
Any substance that dissociates in water to
increase the H+ concentration
BASES:
Any substance that dissociates to
decrease the H+ concentration.
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Biology, Seventh Edition
CHAPTER 2 Atoms and Molecules: The Chemical Basis of Life
pH values
of common
solutions
Copyright © 2005 Brooks/Cole — Thomson Learning
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BUFFERS:
Substance that acts as reservoir for H+.
• Carbonic Acid Buffer System
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