Selenium (Se) - Element 34 | Properties & Electron Configuration
What is Selenium?
Selenium (Se) is element 34, a nonmetal in period 4, group 16. Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴.
| Atomic Number | 34 |
| Symbol | Se |
| Atomic Mass | 78.971 u |
| Category | Nonmetal |
| Period | 4 |
| Group | 16 |
| Block | p |
| Electron Configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴ |
| Short Config | [Ar] 3d¹⁰ 4s² 4p⁴ |
| Electronegativity | 2.55 |
| Atomic Radius | 116 pm |
| Ionization Energy | 941 kJ/mol |
| Electron Affinity | 195 kJ/mol |
| Phase (STP) | Solid |
Electron Configuration
The full electron configuration of Selenium is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴. In noble gas shorthand, this is written as [Ar] 3d¹⁰ 4s² 4p⁴.
Selenium is a p-block element in group 16, period 4.
Periodic Trends
Electronegativity: Selenium has a Pauling electronegativity of 2.55. Within group 16, electronegativity generally decreases down the group.
Atomic Radius: 116 pm. Across period 4, atomic radius generally decreases left to right as nuclear charge increases.
Ionization Energy: 941 kJ/mol. Ionization energy generally increases across a period and decreases down a group.
View all 118 elements with trend overlays for electronegativity, atomic radius, ionization energy, and electron affinity.
Explore Selenium on the Interactive Periodic TableRelated Topics
Oxygen (O)
Properties of Oxygen - same group as Selenium
Sulfur (S)
Properties of Sulfur - same group as Selenium
Tellurium (Te)
Properties of Tellurium - same group as Selenium
Potassium (K)
Properties of Potassium - same period as Selenium
Calcium (Ca)
Properties of Calcium - same period as Selenium
Scandium (Sc)
Properties of Scandium - same period as Selenium