1. Atomic Structure
Protons- positively charged, found in nucleus
Neutrons- neutral, found in nucleus
Electrons- negatively charged, found in electron cloud, In a neutral atom equal to the number of protons
Subatomic particles- smaller particles that make up an atom

2. Atomic Mass Equal to the number of neutrons plus protons
Isotopes are atoms of the same element with different number of neutrons (different masses)
Ex Hydrogen has three isotopes
One with o neutrons, 1 neutrons, 2 neutrons
Atomic mass = proton + neutron -->
1 proton + 0 neutrons = 1 amu (H-1 Isotope)
1 proton + 1 neutron = 2 amu (H-2 Isotope)
1 proton + 2 neutrons = 3 amu (H-3 Isotope)

3. average atomic mass Average atomic mass = (  (% x mass) ) / 100
“S” means summation or addition you are adding the percent times the mass for each isotope
100 is conversion to percentage and has infinite significant figures
 Example:
 Copper consists of two isotopes with masses u (70.5%) and u (29.5%). Calculate the average atomic mass of Cu.
( ( 70.5 x ) + ( 29.5 x ) ) / 100 = 63.6 u

4. Example #1 Average Atomic Mass
Carbon consists of two isotopes with masses u (98.89%) and u (1.11%). Calculate the average atomic mass of Cu.
((98.89* amu)+(1.11* amu))/100 =
( amu amu) / 100 =
amu / 100 = =
12.0 amu

5. Example #2 Average Atomic Mass
Nitrogen consists of two isotopes with masses u (99.63%) and u (.37%). Calculate the average atomic mass of Cu.
((99.63* amu)+(.37* amu))/100 =
14 amu

6. Example #3 Average Atomic Mass
Oxygen consists of three isotopes with masses u (99.759%), u (.037%), and u (.204%). Calculate the average atomic mass of Cu.
((99.759* amu)+(.037* amu)+(.204*17.999))/100 =
( ) /100 = / 100 = amu = 16 amu

7. Example #4 Average Atomic Mass
Sulfur consists of three isotopes with masses u (95.002%), u (.76%), u (4.22%), and u (.014%). Calculate the average atomic mass of Cu.
((95.002* amu)+(.76* amu)+(4.22*33.967)+(.14*35.967)/100 =
( amu amu amu amu ) / 100 = amu /100 = 32 amu