Answer:
16 amu
Explanation:
Given that,
The three common isotopes of oxygen are as follows :
15.995 amu (99.759% abundance), 16.995 amu (0.037 % abundance), and 17.999 amu (0.204 % abundance).
The atomic mass of Oxygen is given as follows :
[tex]Z=\dfrac{15.995\cdot99.759+16.995\cdot0.037+17.999\cdot0.204}{100}\\Z=15.999\ \text{amu}[/tex]
or
Z = 16 amu
Hence, the atomic mass of Oxygen is 16 amu.