34 Se 78.972
Selenium
polyatomic nonmetal
Properties
- Atomic number
- 34
- Atomic mass
- 78.972 u
- Category
- polyatomic nonmetal
- Group
- 16
- Period
- 4
- Block
- p-block
- State (room temp)
- Solid
- Outer-shell electrons
- 6
- Electronegativity
- 2.55 (Pauling)
- Density
- 4.81 g/cm³
- Melting point
- 220.85 °C
- Boiling point
- 684.85 °C
Electron configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴
Noble-gas shorthand: [Ar] 3d¹⁰ 4s² 4p⁴
Electrons per shell: 2, 8, 18, 6, which is 6 in the outermost shell.
Related: electron configuration, the Bohr model, valence electrons.
About Selenium
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.
- Discovered by Jöns Jakob Berzelius
- Appearance: black, red, and gray (not pictured) allotropes
Selenium: frequently asked questions
- What is Selenium?
- Selenium (Se) is the chemical element with atomic number 34. It is a nonmetal (polyatomic nonmetal).
- What is the atomic number of Selenium?
- Selenium's atomic number is 34, which means every Selenium atom has 34 protons in its nucleus.
- What is the electron configuration of Selenium?
- The electron configuration of Selenium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4 (noble-gas shorthand: [Ar] 3d10 4s2 4p4). Its electrons are arranged in shells of 2, 8, 18, 6, with 6 in the outermost shell.
- Is Selenium a metal or a nonmetal?
- Selenium is a nonmetal (polyatomic nonmetal).
- What group and period is Selenium in?
- Selenium is in group 16 and period 4 of the periodic table.
- Is Selenium a solid, liquid, or gas?
- At room temperature, Selenium is a solid.
Position in the periodic table
Data compiled from Wikipedia, PubChem, and IUPAC. Source.