Valency of Curium (Cm)
The valency of Curium is 3 — it has 2 valence electrons, and it loses them to complete its outer shell.
Looking for Curium's valency without wading through a whole chapter? Here is the direct answer first, then the tables and derivations examiners want to see. Every number on this page comes from the same engine that powers the interactive table. Need the whole picture instead — history, characteristics, uses, exam questions? The full Curium page is one click away.
Counting the valence electrons
From the configuration [Rn] 5f⁷ 6d¹ 7s², Curium'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: Curium belongs to the f-block of the periodic table, period 7.
Valency vs valence electrons
Valence electrons are what you count (2 for Curium); 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 Curium from its group?
As an f-block element Curium is not assigned a group; examiners accept its common valency of 3.
Why does Curium show a fixed valency?
Curium has 2 valence electrons and reaches a complete outer shell in one consistent way, so its valency stays fixed at 3.