* Protons and Neutrons: The atomic mass of an element is primarily determined by the number of protons and neutrons in its nucleus.

* Electrons: Electrons have a very small mass compared to protons and neutrons, so we generally don't include them in calculating atomic mass.

Calculation:

* Protons: 8

* Neutrons: 9

* Atomic Mass: 8 + 9 = 17

Therefore, the atomic mass of this element is approximately 17 atomic mass units (amu).

Important Note: This calculation provides an approximate atomic mass. The actual atomic mass of an element is an average based on the relative abundances of its isotopes (atoms with the same number of protons but different numbers of neutrons).