Answer:
9
Explanation:
The atomic mass is defined as the sum of number of protons and the neutrons.
The atomic number is defined as the number of protons in the nucleus.
Here, the number of protons are 4
the number of neutrons are 5
So the sum of number of protons and neutrons = 4 + 5 = 9
Thus, the atomic mass of the element is 9.
