Mendeleev
Periodic table · chemistry · physics
Element story

Argon

Atomic number 18 means that every Argon nucleus contains 18 protons. That proton count is the element's identity: change it and you no longer have Argon.

Start with the nucleus

Atomic number 18 means that every Argon nucleus contains 18 protons. That proton count is the element's identity: change it and you no longer have Argon.

Argon (Ar) is chemical element 18. It belongs to the noble gases, 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 welding, lighting and inert atmospheres.

See the atom

Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.

What this number means

Atomic number 18 means that every Argon nucleus contains 18 protons. That proton count is the element's identity: change it and you no longer have Argon.

Keep exploring

→ Argon · Atomic structure · Periodic trends

18ArArgon
Argon · Ar · Z = 18

Argon (Ar) is chemical element 18. It belongs to the noble gases, and its reference state at room temperature is a gas. Those basic facts are a useful starting point for its chemistry and applications.

Understanding the element

Argon (Ar) is chemical element 18. It belongs to the noble gases, and its reference state at room temperature is a gas. Those basic facts are a useful starting point for its chemistry and applications.

Where do we encounter it?

In practice, it turns up most often in welding, lighting and inert atmospheres.

What its position in the table tells us

Argon sits in period 3, group 18 and the P block. That location is useful because neighbouring elements often share trends in valence electrons, oxidation states and bonding behaviour.