Valency of Astatine (At)
The valency of Astatine is 1 — it has 7 valence electrons, and it loses it to complete its outer shell.
This is the fast lane: one page, one fact, zero digressions. Read the quick answer, check the table, and if your exam needs the full derivation, the sections below walk through it step by step — in Bangla and English, like every page here. Need the whole picture instead — history, characteristics, uses, exam questions? The full Astatine page is one click away.
Counting the valence electrons
From the configuration [Xe] 4f^14 5d^10 6s^2 6p^5, Astatine's outermost shell carries 7 electrons. These are the electrons shown as dots in electron-dot diagrams — the hands Astatine uses to hold other atoms.
Position check: Astatine belongs to group 17 of the periodic table, period 6. For main-group elements in groups 13–18, a quick rule is valency = group number − 10, which gives 7 here.
Valency vs valence electrons
Valence electrons are what you count (7 for Astatine); valency is what the atom will do to complete its outer shell (1 here). Keep the two words straight and half the periodic-table chapter writes itself.
Students also ask
How do I find the valency of Astatine from its group?
Astatine sits in group 17; groups 13–17 follow valency = group − 10, giving 7 (though Astatine also shows 1).
Why does Astatine show a fixed valency?
Astatine has 7 valence electrons and reaches a complete outer shell in one consistent way, so its valency stays fixed at 1.