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Information valid for Ar-40 unless otherwise noted

Basic Information

Symbol: Ar
Atomic Number: 18
Mass: 39.948
Melting Point: -189.3 C
Boiling Point: -186.0 C
Number of Protons/Electrons: 18
Number of Neutrons: 22
Classification: Noble Gas
Crystal Structure: Cubic
Density @ 293 K: 1.784 g/cm3
Color: Colorless Gas

Atomic Structure

[Bohr Model of Argon]
Number of Energy Levels: 3

  1. First Energy Level: 2
    Second Energy Level: 8
    Third Energy Level: 8


Isotope Half Life
Ar-36 Stable
Ar-37 35.0 days
Ar-38 Stable
Ar-39 269.0 years
Ar-40 Stable
Ar-41 1.8 hours


Date of Discovery: 1894
Discoverer: Sir William Ramsey
Name Origin: From the Greek word argon (inactive)
Uses: Lighting
Obtained From: air