Valency of Protactinium (Pa)
The valency of Protactinium is 3 — it has 2 valence electrons, and it loses them 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 Protactinium page is one click away.
Counting the valence electrons
From the configuration [Rn] 5f² 6d¹ 7s², Protactinium's outermost shell carries 2 electrons. For a f-block element the nearby inner "f" subshell can also lend electrons, which is where variable valency comes from.
Position check: Protactinium belongs to the f-block of the periodic table, period 7.
Valency vs valence electrons
Valence electrons are what you count (2 for Protactinium); valency is what the atom will do to complete its outer shell (3 here). Keep the two words straight and half the periodic-table chapter writes itself.
Students also ask
How do I find the valency of Protactinium from its group?
As an f-block element Protactinium is not assigned a group; examiners accept its common valency of 3.
Why does Protactinium show a fixed valency?
Protactinium has 2 valence electrons and reaches a complete outer shell in one consistent way, so its valency stays fixed at 3.