Selenium

Nonmetal

Symbol: Se

Atomic Number: 34

Standard State: Solid

Atomic Mass: 78.97

Electron Configuration: [Ar]4s2 3d10 4p4

Electronegativity: 2.55

Atomic Radius: 190

Ionization Energy: 9.752

Melting Point: 493.65

Boiling Point: 958

Density: 4.809

Year Discovered: 1817