Francium
Atomic number 87 means that every Francium nucleus contains 87 protons. That proton count is the element's identity: change it and you no longer have Francium.
Start with the nucleus
Atomic number 87 means that every Francium nucleus contains 87 protons. That proton count is the element's identity: change it and you no longer have Francium.
Francium (Fr) is chemical element 87. It belongs to the alkali 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 scientific research.
See the atom
Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.
What this number means
Atomic number 87 means that every Francium nucleus contains 87 protons. That proton count is the element's identity: change it and you no longer have Francium.