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 (-)

Basic Chemistry

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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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6

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

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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

11

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)

Basic Chemistry

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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

6

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