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Periodic table · chemistry · physics
Element story

Astatine

Atomic number 85 means that every Astatine nucleus contains 85 protons. That proton count is the element's identity: change it and you no longer have Astatine.

Start with the nucleus

Atomic number 85 means that every Astatine nucleus contains 85 protons. That proton count is the element's identity: change it and you no longer have Astatine.

Astatine (At) is chemical element 85. It belongs to the halogens, 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 scientific research, nuclear medicine and chemical synthesis.

See the atom

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

What this number means

Atomic number 85 means that every Astatine nucleus contains 85 protons. That proton count is the element's identity: change it and you no longer have Astatine.

Keep exploring

→ Astatine · Atomic structure · Periodic trends

85AtAstatine
Astatine · At · Z = 85

Astatine (At) is chemical element 85. It belongs to the halogens, 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

Astatine (At) is chemical element 85. It belongs to the halogens, 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 scientific research, nuclear medicine and chemical synthesis.

What its position in the table tells us

Astatine sits in period 6, group 17 and the P block. That location is useful because neighbouring elements often share trends in valence electrons, oxidation states and bonding behaviour.