Barium
Atomic number 56 means that every Barium nucleus contains 56 protons. That proton count is the element's identity: change it and you no longer have Barium.
Start with the nucleus
Atomic number 56 means that every Barium nucleus contains 56 protons. That proton count is the element's identity: change it and you no longer have Barium.
Barium (Ba) is chemical element 56. It belongs to the alkaline-earth metals, 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 medical imaging equipment, drilling fluids and fireworks.
See the atom
Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.
What this number means
Atomic number 56 means that every Barium nucleus contains 56 protons. That proton count is the element's identity: change it and you no longer have Barium.