1. Chemistry Chapter 3 Section 3
Counting Atoms: Average Atomic Mass

2. Average Atomic Mass Elements are usually mixtures of isotopes
Average atomic mass is weighted average of naturally occurring isotopes of an element
Calculated by taking percent of that isotope times mass of that isotope

3. Calculating Average Atomic Mass Example
Copper
Average atomic mass:
(0.6917)( ) + (0.3083)( )
63.55 amu
Isotope
Percent
Mass (amu)
Copper-63
69.17%
Copper-65
30.83%

4. Your task:
Using the values given in Table 3-4 (p 80), calculate the average atomic mass of:
Hydrogen
Carbon
Oxygen
Show all your work and turn this in!