Oxygen has three different isotopes that occur naturally in different amounts if 99 is oxygen- 16 0.04 is oxygen- 17 and 0.20 is oxygen-18 calculate the relative atomic mass of oxygen?

To calculate the relative Atomic Mass of oxygen, you multiply the mass of each isotope by its natural abundance (in decimal form), and then sum these values. The calculation is as follows:

[ \text{Relative atomic mass} = (16 \times 0.990) + (17 \times 0.0004) + (18 \times 0.0020) = 15.84 + 0.0068 + 0.036 = 15.8868 ]

Thus, the relative atomic mass of oxygen is approximately 15.88 amu.