What is the most common oxidation state of astatine?

The -1 state (astatide, At-) is the most common and stable oxidation state. It mirrors the behavior of other halogens like iodine, forming salts such as CsAt and NaAt.

Can astatine have a positive oxidation state?

Yes. Astatine can exhibit +1, +3, +5, and +7 oxidation states, though these are far less stable than -1. The +1 state appears in compounds like AtF and AtCl. Higher states (+5, +7) require strongly oxidizing conditions and are rarely observed.

Why is astatine so rare and why does that matter for its chemistry?

Astatine is the rarest naturally occurring element; all isotopes are radioactive and short-lived. Most chemical data comes from tracer-level experiments. Its chemistry is often inferred from trends in the halogen group (F, Cl, Br, I, At), where metallic character increases down the group — explaining why At shows more cationic behavior than iodine.

How does astatine compare to iodine in oxidation states?

Both share -1, +1, +3, +5, and +7 states, but astatine's higher states are harder to access and less well-characterized. Astatine's greater metallic character means it is more stable as a cation than iodine, making the +1 state relatively more accessible in At chemistry.

Is astatine used in medicine?

Yes. Astatine-211, which commonly exists as At- in biological systems, is used in targeted alpha therapy (TAT) for cancer treatment. Its -1 state allows it to mimic iodine and accumulate in the thyroid, which is exploited in thyroid cancer radiotherapy research.

Astatine Oxidation States

Name: Astatine Oxidation States
Availability: InStock
Author: Nham Vu

Explore the oxidation states of Astatine (At, Z=85), from the stable -1 state to the rare +7, with examples of compounds and stability notes.

Astatine (At) — Z = 85

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Astatine is a radioactive halogen. All isotopes are unstable; At-211 (t½ 7.2 h) is the most studied for medical use.

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Astatine is the heaviest halogen that occurs naturally (in trace quantities). Its oxidation states range from -1 to +7, mirroring the pattern of lighter halogens but with greater metallic character that makes the positive states more accessible.

All Oxidation States at a Glance

State	Ion / Form	Stability	Key Example

Summary