1. Chapter 2
The Chemistry of Life

2. Matter
A. Anything that has mass and takes up space.
1. Mass – quantity of matter an object has.
Mass stays the same, weight changes.
2. Elements
A. Elements are pure substances that cannot be broken down chemically into simpler matter.
B. Most important elements:
1. Carbon – C
2. Hydrogen – H
3. Oxygen – O
4. Nitrogen – N
An element symbol consists of 1 or 2 letters, first always capitalized, second is lower cased.

4. 3. Atoms
A. Atoms are the simplest particle of an element that retains all of the properties of that element
B. Parts of the atom
1. Nucleus – middle portion where most of
the mass is found
a. Protons – particle with positive charge (p+)
b. Neutron – particle with no charge (n0)
c. Atomic number is related to number of
protons
d. Atomic mass- total mass of protons and neutrons.

5. 2. Electrons - negatively charged particle
located around the nucleus and has very little mass. (Electron cloud area)
a. Electrons are found in energy levels around the outside of the nucleus.
b. Two electrons are held in the lowest
energy level nearest the nucleus.
c. Eight electrons can be held in the next
highest energy level, further from the
nucleus. 18 on the third level and 32 on the 4th level.
d. Protons and electrons will equal at an atoms natural state.

6. 3. Valence
The valence is the furthest energy level from the nucleus on an atom.
The furthest energy level packs the most energy and those electrons will be the one that will either share with another atom or transfer to another atom, during bonding.