Neptunium
Atomic number 93 means that every Neptunium nucleus contains 93 protons. That proton count is the element's identity: change it and you no longer have Neptunium.
Start with the nucleus
Atomic number 93 means that every Neptunium nucleus contains 93 protons. That proton count is the element's identity: change it and you no longer have Neptunium.
Neptunium (Np) is chemical element 93. It belongs to the actinoids, and its reference state at room temperature is a solid. Those basic facts are a useful starting point for its chemistry and applications.
In practice, it turns up most often in scientific research and nuclear science.
See the atom
Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.
What this number means
Atomic number 93 means that every Neptunium nucleus contains 93 protons. That proton count is the element's identity: change it and you no longer have Neptunium.