Element Symbol: Ar

Atomic Mass: 39

Atomic Number: 18

Number of Protons: 18

Number of Electrons: 18

Number of Neutrons: 21

Boiling Point:   -186.0 °C (87.15 K, -302.8 °F)

This is a picture of Argon                               Melting Point:  -189.3 °C (83.85 K, -308.74 °F)

                                                                              Freezing Point:  -189.3 °C (83.85 K, -308.74 °F)

                                                                              Density:  1.784 g/cm³

                                                                              Electronegativity: unknown (pauling)

How was it named?  Sir William Ramsay discovered it in 1894. It comes from the Greek word, Argon which means inactive.

Argon, showing the nucleus, and the electrons in orbitals.