Hydrogen
Atomic number 1 means that every Hydrogen nucleus contains 1 protons. That proton count is the element's identity: change it and you no longer have Hydrogen.
Start with the nucleus
Atomic number 1 means that every Hydrogen nucleus contains 1 protons. That proton count is the element's identity: change it and you no longer have Hydrogen.
Hydrogen (H) is chemical element 1. It belongs to the nonmetals, and its reference state at room temperature is a gas. Those basic facts are a useful starting point for its chemistry and applications.
In practice, it turns up most often in water and the chemistry of life, fertiliser production and oil refining.
See the atom
Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.
What this number means
Atomic number 1 means that every Hydrogen nucleus contains 1 protons. That proton count is the element's identity: change it and you no longer have Hydrogen.