If an Isotope of Oxygen Has 8 Protons, 10 Neutrons

Question

If an isotope of oxygen has 8 protons, 10 neutrons, and 8 electrons, its mass number is
A) 26.
B) 16.
C) 18.
D) 8.
E) 12.

Accepted Answer

The mass number is calculated by adding the number of protons and neutrons in an atom. In this case, adding 8 protons and 10 neutrons gives a mass number of 18. Therefore, the correct answer is (C).