18
Ar
Noble gas

Argon

Atomic number 18 · Period 3 · Block P

Ar · Argon
Mendeleev.com

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.

weldinglightinginert atmospheres
Standard atomic weight[39.792, 39.963]

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.

Worth remembering
Argon has a characteristic place in the periodic table that helps explain both its chemistry and its practical uses

Scientific sources

Element identity
Atomic number18
Group18
Period3
BlockP
CategoryNoble gas
PhaseGas