Boron
Atomic number 5 means that every Boron nucleus contains 5 protons. That proton count is the element's identity: change it and you no longer have Boron.
Start with the nucleus
Atomic number 5 means that every Boron nucleus contains 5 protons. That proton count is the element's identity: change it and you no longer have Boron.
Boron (B) is chemical element 5. 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 borosilicate glass, glass fibre and plant nutrition.
See the atom
Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.
What this number means
Atomic number 5 means that every Boron nucleus contains 5 protons. That proton count is the element's identity: change it and you no longer have Boron.