Selenium (Se)
Selenium (Se, element 34) is a nonmetal in group 16, period 4. Atomic mass 78.971, electron configuration [Ar] 3d¹⁰ 4s² 4p⁴, uses and facts.
About Selenium
Selenium is a nonmetal with the symbol Se and atomic number 34. It is a solid at room temperature, and it sits in group 16, period 4 of the periodic table. Selenium was discovered in 1817 by Jöns Jacob Berzelius.
Selenium key facts
- Atomic number: 34
- Symbol: Se
- Atomic mass: 78.971 u
- Category: nonmetal
- Group: 16
- Period: 4
- State at room temperature: solid
- Electron configuration: [Ar] 3d¹⁰ 4s² 4p⁴
- Electronegativity (Pauling): 2.55
- Melting point: 494 K (220.85 °C)
- Boiling point: 958 K (684.85 °C)
- Density: 4.81 g/cm³
- Common oxidation states: −2, −1, 0, +2, +4, +6
Electron configuration
The electron configuration of selenium is [Ar] 3d¹⁰ 4s² 4p⁴. The part in brackets is the noble gas core; the rest shows how the outer electrons fill their subshells. Selenium has 6 valence electrons.
Uses of selenium
- Glass
- Solar cells
- Dietary supplements
Did you know?
Selenium is essential to human health but toxic in large amounts, a classic example of dose makes the poison.
Other elements in group 16 and neighbours
Frequently asked questions
What is the atomic number of selenium?
The atomic number of selenium is 34, which means every selenium atom has 34 protons.
What is the electron configuration of selenium?
The electron configuration of selenium is [Ar] 3d¹⁰ 4s² 4p⁴.
What group and period is selenium in?
Selenium is a nonmetal in group 16, period 4.
What state is selenium at room temperature?
Selenium is a solid at room temperature.
What is selenium used for?
Selenium is used for glass, solar cells, dietary supplements.