1. The Chemistry of Life Chapter 2
The Nature of Matter
Section 2-1
Biology 102

2. Chemistry Study of chemistry begins with the atom
Atom – basic unit of matter
Means indivisible

3. Atom Contains subatomic particles Proton Neutron Electron
Positive charge
Neutron
No charge
Highest mass
Electron
Negative charge
Constantly in motion and high energy motion keeps electrons outside nucleus

4. Atom Nucleus – Center of atom that contains protons and neutrons
All atoms are neutral
P = E
Atomic # - number of protons
Atomic mass – protons + neutrons

5. Elements and Isotopes
Element – pure substance that consists entirely of one type of atom
Over 100 known
12 common in living organisms
Ex: C, H, N

6. Isotopes
Isotope – atoms of the same element with differing number of neutrons
Identified by their mass numbers (average)
All isotopes have the same chemical numbers
Ex: hydrogen, deuterium, tritium

7. Radioactive Isotopes Unstable nuclei and nuclei break down over time
Radiation is dangerous, but can be advantageous

8. Chemical Compouds Compounds – two or more elements combined together
Ex: H20, NaCl
Physical and chemical properties of the compound differ from the original elements
Ex: NaCl

9. Chemical Bonds Atoms do not have the same ability to attract electrons
Due to this, usually one atom in a bond will pull the electrons closer to it than the other atom.
Creates partial negative and positive charges
Creates van der Waals forces
Slight attraction that develops between oppositely charged regions of nearby molecules.
Ex: Gecko