An ion contains 8 protons, 10 electrons, and 7 neutrons. What is the mass of the ion?

Answer: 15

Explanation:

The mass of the ion is the sum of the protons and neutrons inside its nucleus.

i. e Mass number = protons + neutrons

Mass number = 8 protons + 7 neutrons

= 15

Furthermore, since the number of protons differ from the number of electrons by 2, the ion was formed when its atom gained 2 electrons. Thus, it is a negatively charged ion (anion) with a mass of 15