I. Levels of Biological Organization Smaller & simpler Subatomic particles (n, p, e) Atoms Molecules Organelles Cell Tissues Organs Organ Systems Organism Population Communities Larger & more complex Ecosystem

Chemistry Review & Biochemistry

II. Introduction A. But wait…isn’t this Biology? Yes, but we need to understand the basic structure of atoms, because atoms make up molecules.

B. Matter anything that has mass and takes up space 1. All matter is made out of the 115 or so elements, which are listed on the Periodic Table (PT) 2. Elements cannot be broken down into a substance with a different chemical or physical property, unlike molecules. a. Example: water (H20) can be broken down into the elements hydrogen and oxygen. However, hydrogen and oxygen have totally different properties than water.

II. Atom smallest particle of an element that keeps the properties of the element A. Structure 1. 3 particles (they’re called subatomic particles) Abbreviation Location Mass (amu) Charge Proton p+ or + Nucleus 1 +1 Neutron n0 or 0 Electron e- or - Energy levels 1/1840 -1

2. Bohr Model Nucleus e- e- p+ n0 Energy Levels

3. 99% of the mass of an atom is in the nucleus 4. Electrons (e-) are always moving 5. e- in the outermost energy level are called valence electrons (VE) 6. To figure out how atoms will bond, we care about e- (especially VE)

7. Drawings of atoms (Shell Drawings) a. Oxygen atom 8 p+, 8n0, 8e-

b. Nitrogen atom 7 protons, 7 neutrons, 7 electrons

c. Sulfur atom __ protons, __ neutrons, __ electrons 16+ 16 0 2 e- 8 e- 6 e-

d. Hydrogen 1 p+, 0 n0, 1 e-

III. The Periodic Table Organization A. The Periodic Table (PT) lists all of the elements in the world B. There are about 109 elements in the world. This means that everything in the whole world is made out of these elements! C. The Periodic Table is organized into groups and periods. We number groups across the top and the periods along the side. There are 18 groups and 7 periods (see PT).

D. Comparing Oxygen and Sulfur 1. Look at the shell diagrams for Oxygen and Sulfur. What do these atoms have in common? ___________________________________ 2. Locate these 2 atoms on the PT. You should notice that these 2 elements are in the same group. Elements in the same group have the same number of valence electrons. The number of valence electrons is the same as the group number. Elements within the same group will act the same chemically.

IV. Interpreting the Periodic Table A. Information you can figure out by looking at the Periodic Table: Atomic Number Element Symbol Element Name Atomic Mass 17 Cl Chlorine 35.453

B. The atomic mass tells you the mass of an atom in amu (# of protons + # of neutrons). C. The number of protons will equal the number of electrons in an atom D. # of neutrons = atomic mass – atomic number (# or protons) E. Draw a shell diagram for a Chlorine atom, using the information from above. (see back)

F. Draw a shell diagram for a Carbon atom (use the PT)

G. Dot Diagrams for Atoms 1. In a dot diagram, the dots represent the valence electrons. 2. There will not be more than 8 valence electrons. 3. Each unpaired electron is a bonding site. 4. Dot Placement: X O Cl C 1 2 5 3 8 6 4 7

V. Molecules A. 2 basic types of bonds: 1. Ionic chemical bond formed by the attractive forces between 2 ions of opposite charge a. Salt (NaCl)

2. Covalent chemical bond formed when 2 atoms combine by sharing e- a. Water (H20)

3. Why would atoms want to bond? a. In order to become more stable b. An atom defines stability as having 8 valence electrons c. Covalent bonds form molecular compounds. In molecular compounds, atoms share e- to become stable.

B. A closer look at water 1. Dot diagrams: H H O 2. Hydrogen always makes one bond (one unshared e-) 3. Oxygen always makes two bonds (2 unshared e-) 4. Carbon always makes four bonds (4 unshared e-)

C. Dot diagrams for some simple compounds 1. First draw the dot structures for the following atoms (remember: you will need to use the PT) 2. Next to each dot diagram, write the # of bonds that this atom will always make when it is a compound