To determine the name and atomic number of the element with a mass number of 17 and nine neutrons, we can start by subtracting the number of neutrons from the mass number.
The mass number (A) represents the sum of protons (atomic number, Z) and neutrons (N) in an atom. Therefore, A = Z + N.
In this case, the mass number is 17, and the number of neutrons is 9. Subtracting 9 from 17 gives us:
17 - 9 = 8.
The result, 8, corresponds to the atomic number (Z) of the element.
To identify the element with atomic number 8, we can refer to the periodic table. Atomic number 8 corresponds to oxygen (O).
Therefore, the element with a mass number of 17 and nine neutrons is oxygen (O).