Argon has eight valence electrons. Its electron configuration is 1s2 2s2p6 3s2p6, so it has three filled electron shells of 2, 8 and 8. The atomic number of argon is 18.
Argon was discovered by Sir William Ramsay in 1894. It is a nonmetal and a gas at room temperature. Because its outer electron shell is full, it is chemically unreactive. It is a noble gas and belongs to period 3 and group 18 of the periodic table.
Argon has 22 neutrons in its nucleus, and the atomic weight of argon is 39.948 atomic mass units. Its melting point is -308.83 degrees Fahrenheit.