1. Intro to Chemistry I. Atoms A. Smallest whole particle of matter
B. Parts of an atom (subatomic particles)
1. Protons: + charge
Nucleus (99% of atom mass)
2. Neutrons: neutral
3. Electrons (electron cloud): - charge (2000X smaller)
C. Diagram

2. D. Electrons orbit in different energy levels called “shells”
1. Like lanes of a race track
2. Each shell holds a limited number of electrons N
Max e-
Shell M K 2 L K L 8 M 18 N 32
***Inside shells fill first

3. E. Atoms are mostly empty space (Rutherford, 1871)
99% of particles
1% of particles

4. F. Atoms can be electrically charged
1. If protons = electrons neutral atom
2.Protons do not = electrons ion (charged atom)

5. G. 117 Different Types of Atoms (92 naturally occurring and 5 are common to life: C.H.O.N.S.)
1. Identified by the number of protons
Hydrogen: 1
Helium: 2
Oxygen: 8
2. Element – atoms with the same number of protons
a. Pure; cannot be broken down (ex. Gold)
3. Isotope – same number of protons, different number of neutrons

6. H. All Elements are Organized on a Periodic Table
I. The symbol and other info about the element is in each box
Atomic Number - # of protons
Atomic Symbol
Atomic Mass – Protons + Neutrons