The atomic mass of an element whose atoms consist of eight protons, nine neutrons, and eight electrons is
(ignore the periodic table entry for this element and only consider what the atomic mass would be given the number of
subatomic particles in this question).

The atomic mass is: 17

Explanation:

The atomic mass of a compound is calculated as the sum of protons and neutrons. In this case:

Atomic mass = protons + neutrons = 8 + 9 = 17.

Atoms with the same atomic number (Z) but different atomic mass (A) are called isotopes, that is, they differ in the number of neutrons. Example: Hydrogen, Titrio and Deuterium.