1. Atomic Structure Nucleus – contains protons and neutrons
Neutron – particle with no charge
Quarks – particles that make up protons and neutrons
Electron Cloud – area where electrons are found
Proton – positively charged particle

2. C 6 Carbon 12.0 Atomic Number Chemical Symbol Element Name Atomic Mass
- the number of protons
- usually the smallest number C
Chemical Symbol
Carbon
Element Name
12.0
Atomic Mass
- usually the largest number

3. Atomic Number – the number of protons in an individual atom
examples:
Hydrogen : 1 proton
Oxygen : 8 protons
Mass number – the total of protons and neutrons in an atom
# of neutrons = mass number – atomic number
Carbon protons, 6 neutrons
Oxygen-17 – 8 protons, 9 neutrons

4. Isotopes – atoms of the same element that have different numbers of neutrons
For example,

6. Atomic Mass – the weighted average of the masses of all the naturally occurring isotopes of an element
amu – atomic mass unit – unit for atomic mass
Each proton and neutron has a mass of approximately 1 amu
example – Chlorine-35 makes up 76% of all chlorine in nature, and chlorine-37 makes up the other 24%:
(35 x 0.76) = 26.60
(37 x 0.24) =
35.48 amu