Selenium · Se Selenium
is used in the optoelectronic materials and glass industries and is also a trace element with a narrow nutritional safety window.
- atomic number / Atomic number
- 34
- atomic weight / Atomic mass
- 78.97 u
- Family/Group
- 16
- Period · Block / Period · Block
- 4 · p
- Category / Category
- Other non-metals · Nonmetal
- State / State
- solid state
- Electron configuration
- [Ar]4s2 3d10 4p4
- Oxidation states / Oxidation states
- +6, +4, -2
- Electronegativity / Electronegativity
- 2.55（Pauling）
- Density / Density
- 4.809 g/cm³
- Melting point / Melting point
- 493.65 K
- Boiling point / Boiling point
- 958 K
- Atomic radius / Atomic radius
- 190 pm（van der Waals）
- First ionization energy
- 9.752 eV
- Discovery year / Discovery
- 1817
attribute description and data source
properties taken from PubChem periodic table snapshot (2026-10-04). Atomic weights may be reference values or representative isotope masses and cannot be considered exact constants for all samples; density, phase transition points, and phase states depend on temperature, pressure, and allotropes. The solidification of helium requires pressure. Some properties of radioactive and superheavy elements are predicted values, and missing items are marked as not included. Please check the original source and experimental conditions for precise calculations.