Mendeleev
Periodic table · chemistry · physics
Element story

Selenium

Atomic number 34 means that every Selenium nucleus contains 34 protons. That proton count is the element's identity: change it and you no longer have Selenium.

Start with the nucleus

Atomic number 34 means that every Selenium nucleus contains 34 protons. That proton count is the element's identity: change it and you no longer have Selenium.

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.

In practice, it turns up most often in special glasses, electronics and biology.

See the atom

Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.

What this number means

Atomic number 34 means that every Selenium nucleus contains 34 protons. That proton count is the element's identity: change it and you no longer have Selenium.

Keep exploring

→ Selenium · Atomic structure · Periodic trends

34SeSelenium
Selenium · Se · Z = 34

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.

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.

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.