chapter 2 basic chemistry nixon - lane library · atomic structure atoms – smallest units of...
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Basic Chemistry
1Chapter 02
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Chapter 2
Basic Chemistry
Vital Force - Vitality
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• Organisms composed primarily (96%) of only four elements
– Carbon, Oxygen, Hydrogen, Nitrogen
– COHN
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Atomic StructureAtoms – Smallest units of elementsConsist of 3 subatomic particles
Protons (+)Neutrons (no charge)Electrons (-)
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• Each element represented by unique
atomic symbol
– One or two letters
– First letter capitalized
– Atomic #
– Mass #
• Unit of measure is a Dalton
Atomic Symbols
MassMassNumberNumber
AtomicAtomicNumberNumber
AtomicAtomicSymbolSymbol
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Carbon
C
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• Isotopes:
– Atoms of the same element with a differing numbers of neutrons
– Still has same # of protons
Isotopes
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Radioisotopes
– Some isotopes spontaneously decay
• Unstable nucleus
• Radioactive decay transforms one element into another (i.e. Carbon-14 into Nitrogen-14)
• Give off energy in the form of rays and subatomic particles
• Dating
– Half life of C-14 (5.7k years)
• Can be used as tracers (Iodine*)
• Mutagenic – Can cause cancer
Basic Chemistry
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Some Medical Uses forLow Level Radiation
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Electrons
• In neutral atoms p = e- (+ balances -)• Electrons are attracted to the positive nucleus
– Revolve around nucleus in orbitals
• Energy Levels (aka: electron shells) “Bohr Model”– concentric circles around the nucleus– 1st Shell: 2 e-– Subsequent Shells: 8 e-
• (Octet Rule)• Goal = have full outer shell Reactive?? Why
– Hydrogen: 1 shell, goal = 2 e-– All other atoms, goal = 8 e-
• How can an atom be neutral but unstable?• So how do I become stable? Hmmmm
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Bohr Models of Atoms
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Organization of Periodic Table • Elements grouped in periodic table based
on characteristics
– Vertical columns = groups
– Horizontal rows = periods
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Periodic Table (Revisited)Vertical columns indicate
number of electronsin outermost shell
1
H1.008
3
Li6.941
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Na22.99
19
K39.10
4
Be9.012
12
Mg24.31
20
Ca40.08
5
B10.81
13
Al26.98
21
Ga69.72
6
C12.01
14
Si28.09
22
Ge72.59
7
N14.01
15
P30.97
23
As74.92
8
O16.00
16
S32.07
24
Se78.96
9
F19.00
17
Cl35.45
25
Br79.90
10
Ne20.18
18
Ar39.95
26
Kr83.60
2
He4.003
1
2
3
4
Horizontal periods indicate
total number
of electron shells
I
II III IV V VI VII
VIII
Practice!!!
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Elements and Compounds
• Molecule vs. Compound
• Characteristics dramatically different from
constituent elements (WHY?)
Basic Chemistry
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Formulas and Equations
• Chemical formula – describes composition of a compound
– Ex: water = H2O
(2 hydrogen atoms + 1 oxygen atom)
• Chemical Equations – describes reaction
between atoms and compounds
– Ex: combustion
– C3H8 (propane) + 5O2 � 3CO2 + 4H2O + energy
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Shape of molecules
• Are 3D, though look 1D on paper
• Final shape of molecule determines its biological role.
– Examples: enzymes, antibody/antigen
recognition, hormones
• receptor cells recognize hormone insulin
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Types of Bonds: Ionic Bonding
• What interacts?• Ionic Bonds
– Octet rule:• Atoms “want” 8 electrons in outer shell
– How to determine if an element will donate or accept?
Basic Chemistry
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Covalently
Bonded Molecules
-When atoms share electrons-Outer orbitals overlap-Strong and stable-Each atom has complete outer e- shell
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Nonpolar Covalent Bonds
• Electrons are equally shared between
atoms
– ex: Methane (CH4)
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Polar Covalent Bonds• e- unequally shared between 2 atoms
• Why does this occur?
– Electronegativity
• Ex: water molecule (H2O) is “polar”
– Atoms assume slight change
Basic Chemistry
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• Weak Bond but…
Hydrogen Bonding (VIDEO)
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Properties of Water
• All of the following properties are caused by ?
• High Heat Capacity
• High Heat of Vaporization
• Universal Solvent
• Cohesive & Adhesive
• High Surface Tension
• Less Dense in Frozen State
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The Chemistry of Water: Heat Capacity
– Temperature/Heat/Kinetic Energy
• Water has a high heat capacity (specific heat)
– Specific Heat Definition: ______________________
– Water has a SH of 1 calorie
• Thermal inertia – resistance to temperature change
– Slow change in temp (prevents rapid temp. fluctuations)
– What causes this??
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Heat of Vaporization (Evaporation)
• High heat of vaporization
– To raise water from 97-98 ºC; ~1 calorie
– To raise water from 98 to 99 ºC; ~1 calorie
– However, large numbers of hydrogen bonds must be broken to evaporate/vaporize water
– To raise 1g water from 99 to 100-101 ºC; ~540 calories!
• Uses:
• 1) Evaporative Cooling (sweating)
– % Humidity
• 2) Moderate coastal temperatures!
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Water as a Solvent
• Solutions consist of:
– Solvent vs. Solute
• Ionic compounds dissociate in water
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Polar compounds readily dissolve; hydrophilicEx: Ammonia
Nonpolar compounds do not dissolve; hydrophobic(fats, gasoline, oils)
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Unusual Density
• Frozen water less dense than liquid water
• Max density = 4’C, below that will expand– Sodas in freezer
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Water Properties Continued
• Cohesive and Adhesive
– Cohesion – water to water
– Adhesion – water to polar surfaces
• High Surface Tension
– Caused by hydrogen bonds
– Who cares???
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Water as
a Transport
Medium
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pH of Water:
Acids• Water Ionizes (draw out) – pH of Water
• Acids – dissociate in water to give H+ ion and an
anion (Proton Donor)
– HCl
• Bases – release OH- ions or take up hydrogen ions (H+)
– NaOH
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Fig. 3-9
Neutralsolution
Acidicsolution
Basicsolution
OH–
OH–
OH–
OH–
OH–OH–
OH–
H+
H+
H+
OH–
H+ H+
H+ H+
OH–
OH–
OH–OH–
H+
OH–
H+
H+
H+
H+
H+
H+
H+
OH–
Neutral[H+] = [OH–]
pH Scale
0
1
2
3
4
5
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7
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Battery acid
Gastric juice,lemon juice
Vinegar, beer,wine, cola
Tomato juice
Black coffee
Rainwater
Urine
Saliva
Pure water
Human blood, tears
Seawater
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10
Milk of magnesia
Household ammonia
Householdbleach
Oven cleaner
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12
13
14
pH scale
Measures concentration of H+
[H+][OH-] = 10-14
Scale from 0 to 14
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pH Scale
• Logarithmic scale
• Each pH value represents 10X change in
concentration of H+ and OH-
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The pH Scale
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Buffers in Biology
• Help maintain pH (blood pH ~ 7.4)
• Donate protons when pH becomes too
basic
• Accept protons when pH becomes too
acidic
• Carbonic Acid/Bicarb in Blood