Oxygen
Atomic number 8 means that every Oxygen nucleus contains 8 protons. That proton count is the element's identity: change it and you no longer have Oxygen.
Start with the nucleus
Atomic number 8 means that every Oxygen nucleus contains 8 protons. That proton count is the element's identity: change it and you no longer have Oxygen.
Oxygen (O) is chemical element 8. It belongs to the nonmetals, and its reference state at room temperature is a gas. Those basic facts are a useful starting point for its chemistry and applications.
In practice, it turns up most often in respiration, metallurgy and steel and water treatment.
See the atom
Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.
What this number means
Atomic number 8 means that every Oxygen nucleus contains 8 protons. That proton count is the element's identity: change it and you no longer have Oxygen.