I. Chemistry. A. Elements and Atoms 1. Elements- Substance which cannot be broken down into a...

I. Chemistry

A. Elements and Atoms

1. Elements- Substance which cannot be broken down into a simpler substance

A) 96% of all life is Carbon, Hydrogen, oxygen and nitrogen

B) 3.2% Calcium, Phosphorous, Potassium and Sulfur

2. Atom- The smallest particle of an elementa) Atomic structure

1. Proton- positively charged. In nucleus. 1 Dalton mass

2. Neutron- neutral charge. In nucleus. 1 Dalton mass

3. Electron- negative charge. Orbits nucleus. 1/2000 Dalton mass

b) Electron Energy Levels

Energy Level Maximum Number of Electrons

1st (K)

2nd (L)

3rd (M)

4th (N)

2) However, the outer energy level: the valence shell will never hold more than 8 electrons

1)

2 electrons

8 electrons

18 electrons

32 electrons

3. Periodic Table- Chart of Elements arranged by proton number and valence electrons

8

OOxygen

15.9

e) Neutron Number = Atomic mass – Atomic number

a) Atomic Number- indicates the number of proton(s) which determines the identity of the element

b) Symbol- Identifies the element

c) Atomic Mass- the mass of the atom in Daltons.

d) Atoms are Neutral- Therefore the number of proton and electrons are equal

4. Bohr Diagrams- illustrations of an atom. Example: Oxygen

8p

8n

6e2e

5. Isotopes- Atoms with extra neutrons. Some are unstable and give off radiation as they decay

Number of electrons in 2nd energy level

Electrons in the first energy level

Nucleus with the number of protons in & neutrons

B. Chemical Bonding

1. Compound- two or more elements chemically combined

2. Molecule- smallest particle of a compound

H2O 2CO2 C2H5OH C6H12O6

Atoms

Elements

Molecules

3

2 2 3

9

1

6

2 1 1

24

3

What Determines Whether Atoms Bond?

3. Atoms with their outer energy level filled are stable. He, Ne, Ar, Kr, Xe, Rn (Noble Gasses). Keep in mind that helium’s first energy level is its outer energy level and therefore requires only two electrons in its valence shell for stability

4. Unstable atoms will share or transfer electrons to become stable

C. Covalent Bonding- Sharing a pair of electrons to fill the outer energy level

p

p

P8

n8

2e-

e-

e-

e-

e-

e-

e-

OxygenHydrogen

Hydrogen

e-

e-

Example of Ionic Bonding

Valence Electrons =Sodium’s Electronegativity =

Valence Electrons =Chlorine’s Electronegativity =

Electron Transfer

1 7

0.93 3.16

Electronegativity Difference = 2.23 > 1.67

Attraction

Sodium

Atom AtomChlorine

Ion Ion

D. Ionic Bonding- The transfer of electrons from one element to another to fill the outer energy level

1. Electronegativity- a measure of the attraction of electrons to an atom.

2. When atoms with high electrogenativities are placed with atoms with low electronegativities (the difference is greater than 1.67), Ionic bonding occurs

a) The transfer of the electron from one atom to another causes the formation of particles called ions

b) Ions with opposite charges attract

E. Hydrogen Bonds- weak bonds between polar molecules

1. When atoms with different electronegativites covalently bond, electrons are shared unequally resulting in polar covalent bonds.

2. Hydrogen bonds can then for between the molecules or even parts of large molecules like DNA and proteins

“Many have lived a life without love, not one without water.”

F. Water’s Importance to Life

1. All living things contain a large amount of water. Ex. Humans are 60-65% water

2. Living things are essentially water solutions

A) Solution- a solute dissolved in a solventB) Concentration- the amount of solute in the

solventC) Solutions are mixtures. The solute and the

solvent do not chemically combine

3. The Properties of Water

a. Cohesion- water molecules cling to each other. This aids in the transport of water in plants

Adhesion

b. Adhesion- water molecules cling to other substances. Aids in the transport of water in plants

c. High Heat Capacity- water resists changes in temperature. Moderates global temperatures

d. Water Expands when it Freezes- ice is less dense than liquid water. Insulates water in winter keeping it in liquid form

e. Water is an excellent solvent most substances dissolve in water. Allows for nutrient transportation in organisms

f. Water is clear- this allows light to penetrate to aquatic plants

G. Acids, Bases and pH

1. Acids- release H+ ions (hydrogen ions) in solution

2. Base- release OH- ions (Hydroxide ion) in solution

3. pH Scale- measure of the H+ ions in a solution

Acids, Bases and pH1. Dissociation of water molecules (H2O H+ +

OH-) is a rare occurrence. Only one molecule of water is disassociated per 554 million water molecules.

2. Thus, at 25oC, the number of hydrogen ions (H+) and hydroxide ions (OH-) is equal at 10-7 M.

3. In any solution, the sum of the OH- ions and H+ ions is 10-14

4. The concentrations of hydrogen ions and hydroxide ions are exactly inverse! Increase one and you will decrease the other.

5. The pH scale is based on the power of 10

You Try a Problem

If an acid was added to water to increase the hydrogen ion concentration to 10-5, what would be the hydroxide ion concentration? What would be the pH?

If base was added to a solution until the hydroxide ion concentration was 10-3, what would be the hydrogen ion concentration? What would be the pH?

If the pH of a solution is 6, what is the hydrogen ion concentration? What is the hydroxide ion concentration?

H. Chemical Reactions- breaking of existing bonds and the formation of

new ones

1. Activation Energy- energy needed to start a reaction. (heat, stirring, electric.)

2. Atoms cannot be created or destroyed in a chemical reaction, they are only rearranged into different molecules

3. Example: H2 + O2 H2O

Reactants yields Products

 2H2 + O2 2 H20

coefficient

Subscript

4. Endergonic Vs Exergonic Reactions