Given that oxygen has an atomic number of 8.

How many protons and neutrons are in the isotope 18^O, or oxygen - 18?

Answer: 8 protons and 10 neutrons

Explanation:

Atomic number is defined as the number of protons or number of electrons that are present in an atom.

Atomic number = Number of electrons = Number of protons

atomic number = 8 = Number of protons

Mass number is defined as the sum of number of protons and neutrons that are present in an atom.

Mass number = Number of protons + Number of neutrons

Mass number = 18 = Number of protons + Number of neutrons

Thus Number of neutrons = 18 - Number of protons = 18 - 8 = 10

Thus there are 8 protons and 10 neutrons in Oxygen - 18.

Oxygen (O), for example, has three naturally occurring isotopes, which can be written as 8/16O, 8/17 O, and 8/18O.