Answer:
The atomic mass is: 17
Step-by-step explanation:
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The atomic mass is the sum of the number of protons and neutrons in the nucleus of the atom. The electrons do not count because they are not present in the nucleus.
In this case there are 8 protons and 9 neutrons. The mass is:
8 + 9 = 17
We conclude that the atomic mass is: 17