# What is the atomic number of most atoms of oxygen? What is the mass number of most atoms of oxygen?

Mar 8, 2016

$Z$, the atomic number of ALL oxygen atoms is $8$. Most oxygen is the ""^16O isotope.

#### Explanation:

The atomic number, the number of massive, positively-charged nuclear particles, defines the identity of the element. $Z$ $=$ $6$, the element is carbon, $Z$ $=$ $7$, the element is nitrogen, BUT $Z$ $=$ $8$, the element is OXYGEN.

The oxygen nucleus usually contains $8$ neutrons (so ""^16O is the most common isotope), but ""^17O and ""^18O are stable. (How many neutrons does each species contain?)

The thing to remember is the atomic number, $Z$. $Z$ defines the identity of the element. In fact you don't even have to remember $Z$, as a Periodic Table will be supplied in all your examinations.

How does oxygen occur in the natural world?