If an element has an atomic number of 8 and an atomic mass number of 18, would it be an isotope? Why or why not?

It would be an isotope.

Background Information:

Isotopes are typically elements that have a different number of protons than neutrons. The atomic mass is the total number of protons and neutrons. The atomic number is the number of protons.

Explanation:

If the atomic number is the number of protons that means that this particular element has 8 protons. If the atomic mass is the total number of protons and neutrons then we can simply take away the amount of protons from that number, 18 - 8 = 10. If we take protons away from the number of protons and neutrons we are left with the number of neutrons. So there are 10 neutrons. Because there are 8 protons and 10 neutrons, or a different amount of neutrons and protons we know that this particular atom is an isotope.

it's c (engineer's do their work with mechanical stuff not on any living being)