Atomic Number
18
Element 18
Argon (Ar)
Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas.
Atomic Mass
39.948 u
Category
Noble Gas
Period
3
Group
Group 18: noble gases
Phase
gas
Density
0.0017837 g/cm3
Electron Shells
2, 8, 8
Atomic Structure
Protons: 18. Electrons: 18. Neutrons: Varies by isotope.
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶
Why Argon Matters
Argon helps connect atomic number 18, noble gas behavior, period 3 trends, and electron shell structure. Its gas phase, atomic mass of 39.948 u, and electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ make it useful for comparing bonding patterns across the periodic table.
Discovery and Occurrence
Argon was discovered 1894 by Lord Rayleigh, William Ramsay. Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas.
Safety and Handling Context
Argon is a noble gas and is generally chemically inert. The main safety concern for many gases is displacement of breathable air in confined spaces.
Related Elements
Frequently Asked Questions
- What is the atomic number of Argon?
- Argon has atomic number 18, which means a neutral atom has 18 protons and 18 electrons.
- What is the chemical symbol for Argon?
- The chemical symbol for Argon is Ar.
- What category is Argon in?
- Argon is classified as a noble gas and sits in period 3 of the periodic table.
Explore Argon in 3D
Use the interactive table above to rotate atomic models, compare periodic trends, and move from Argon to neighboring elements without losing your place.