Antimony
Atomic number 51 means that every Antimony nucleus contains 51 protons. That proton count is the element's identity: change it and you no longer have Antimony.
Start with the nucleus
Atomic number 51 means that every Antimony nucleus contains 51 protons. That proton count is the element's identity: change it and you no longer have Antimony.
Antimony (Sb) is chemical element 51. It belongs to the metalloids, 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 flame retardants, alloys and semiconductors.
See the atom
Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.
What this number means
Atomic number 51 means that every Antimony nucleus contains 51 protons. That proton count is the element's identity: change it and you no longer have Antimony.