1. Biology and Human Concerns
09/16/09 – Notes
Basic Chemistry (Chapter Two)
Chemical Elements
Element => substance that cannot be broken down to other substances by
chemical reactions
Compound => substance consisting of two or more elements combined in
a fixed ratio. Water = H2O two hydrogen atoms affixed to an oxygen atom
Sodium + Chlorine = sodium chloride = table salt
Atoms and Molecules
Subatomic particles:
-Neutrons
-Protons (ex. Bowling ball)
-Electrons (ex. Ping pong ball)
Atomic Number
-the number of protons
Atomic Mass (Mass number)
-Neutrons plus Protons
--Same charges repel, opposite charges attract—
page 20
Isotopes
-Some atoms of a given element have more neutrons than others
ex. 12C is the most common form of carbon, stable. 13C also stable.
14
C is an unstable “radioactive isotope” of carbon (heavier)
2. -Radioactive tracer used to determine how much DNA is made at different
temperatures
Diagram on page 22—partial periodic table
