How do you calculate the average atomic mass of oxygen 99.76 of atoms with mass of 15.99 amu. .038 with mass of 17 amu.. 0.20 with mass 18.0amu?

To calculate the average Atomic Mass of oxygen, multiply the mass of each isotope by its relative abundance (as a decimal), and then sum the results. For the given isotopes:

[ \text{Average atomic mass} = (0.9976 \times 15.99) + (0.00038 \times 17) + (0.0020 \times 18.0) ]

Calculating this gives:

[ (0.9976 \times 15.99) + (0.00038 \times 17) + (0.0002 \times 18) \approx 15.999 ]

Thus, the average atomic mass of oxygen is approximately 15.999 amu.