34 Se 78.9718

Selenium

POLYATOMIC NONMETAL

Phase: Solid

Discovered: Jöns Jakob Berzelius

Block: P

Summary

Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between those of its periodic table column-adjacent chalcogen elements sulfur and tellurium. It rarely occurs in its elemental state in nature, or as pure ore compounds.

Appearance: black, red, and gray (not pictured) allotropes

Source: Wikipedia

Physical Properties

Atomic Mass 78.9718 u

Density 4.81 g/cm³

Melting Point 494 K

Boiling Point 958 K

Molar Heat 25.363 J/(mol·K)

Electron Affinity 194.9587 kJ/mol

Ionization Energies

1^st: 941 kJ/mol

2^nd: 2045 kJ/mol

3^rd: 2973.7 kJ/mol

4^th: 4144 kJ/mol

5^th: 6590 kJ/mol

6^th: 7880 kJ/mol

7^th: 14990 kJ/mol