Element 34
Selenium
Nonmetals
Selenium (Se) is in the p-block of the periodic table — group 16, period 4.
Selenium is a chemical element with symbol Se and atomic number 34.
Key data
- Atomic number
- 34
- Atomic mass
- 78.972 u
- Group / Period
- 16 / 4
- Block
- p-block
- Phase at STP
- Solid
- Density
- 4.81 g/cm³
- Melting point
- 220.9 °C
- Boiling point
- 684.9 °C
- Electron configuration
- [Ar] 3d10 4s2 4p4
Periodic table block
Selenium is in the p-block (group 16, period 4). Elements land in the p-block when their highest-energy electrons fill a p subshell — this region holds most nonmetals, the metalloids, and the metals on the right of the table.
New to this? Periodic table blocks explained: s, p, d, and f
Common uses
- •Glass tinting
- •Photocopiers
- •Antioxidant supplements
Discovery
Year: 1817
Discovered by: Jöns Jakob Berzelius
Frequently asked questions
What is the atomic number of Selenium?
Selenium has atomic number 34. Its symbol is Se and its atomic mass is 78.972 u.
What category of element is Selenium?
Selenium is classified as nonmetals. It sits in group 16, period 4 of the periodic table.
What block of the periodic table is Selenium in?
Selenium is in the p-block (group 16, period 4). Its highest-energy electrons occupy the p subshell — you can see this in its electron configuration, [Ar] 3d10 4s2 4p4.
What is Selenium used for?
Common uses of Selenium include: Glass tinting, Photocopiers, Antioxidant supplements.
When was Selenium discovered?
Selenium was discovered in 1817 by Jöns Jakob Berzelius.
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