1. Chemistry All matter is made up of atoms
Atoms: smallest unit of matter
Elements: pure substances that can not be broken down into smaller particles
Compounds: substances that are made up of 2 or more elements in a fixed proportion
Atoms make up elements, elements make up compounds

2. Atom Contents Atoms contain 3 subatomic particles:
Name Charge Location Mass
Proton Nucleus 1 a.m.u.
Neutron Nucleus 1 a.m.u.
Electron – Orbital 0 a.m.u.
A.M.U – atomic mass unit
2 locations in an atom:
Nucleus – located in the center of the atom.
Orbital (shell) – path around the nucleus that contains the electron(s)
Orbital

3. The Periodic Table
A table of all known elements in their non-reacting state
The position in the table indicates key information for an element.
The number in each box that increases by 1 when the table is read left to right is called the atomic number.
The other number found in the box (usually at the bottom of the box) is the atomic mass.

4. Determining Contents of Atoms
3 rules to determine the number of Protons, Neutrons, and Electrons:
Atomic number = # of protons
Number of protons = # of electrons
# Neutrons = Atomic Mass - # protons

5. Determining Contents of Atoms
Atomic number = # of protons
Number of protons = # of electrons
# Neutrons= Atomic Mass - # Protons
Determine the number of protons, neutrons, and electrons for Hydrogen using the 3 rules above:
H – Hydrogen Atomic Number = 1
Atomic Mass = 1
Protons = 1
Electrons = 1
Neutrons = 0

6. Isotopes
Isotopes are naturally occurring elements with the same # of protons & electrons, but a different # of neutrons
Has a different atomic mass
Usually radioactive (unstable)
Power plants – Uranium
Medicine – MRI, diagnostic tracers, cancer treatments
Radioactive (carbon) Dating – determining the age of objects
Ex: 1H – mass 1 a.m.u.(Protium) Normal hydrogen
2H – mass 2 a.m.u. (Deuterium)
3H – mass 3 a.m.u. (Tritium)
Isotopes of Hydrogen

7. Contents of Atoms
Determine the atom contents of the following elements:
Oxygen
Titanium
Helium
Neon