The atomic number (Z) of an element represents the number of protons in its nucleus. In this case, the atomic number is 8.
The mass number (A) of an element represents the total number of protons and neutrons in its nucleus. In this case, the mass number is 17.
To determine the number of neutrons, we subtract the atomic number from the mass number:
Number of neutrons = Mass number (A) - Atomic number (Z)
Number of neutrons = 17 - 8 = 9
Therefore, the element with an atomic number of 8 and a mass number of 17 has 9 neutrons.