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Understanding the element
Selenium (Se) is chemical element 34. It belongs to the nonmetals, and its reference state at room temperature is a solid. Those basic facts are a useful starting point for its chemistry and applications.
Where do we encounter it?
In practice, it turns up most often in special glasses, electronics and biology.
special glasseselectronicsbiology
Standard atomic weight78.971(8)
What its position in the table tells us
Selenium sits in period 4, group 16 and the P block. That location is useful because neighbouring elements often share trends in valence electrons, oxidation states and bonding behaviour.
Worth remembering
Selenium has a characteristic place in the periodic table that helps explain both its chemistry and its practical uses
Selenium has a characteristic place in the periodic table that helps explain both its chemistry and its practical uses