Valency of Erbium (Er)
The valency of Erbium is 3 — it has 2 valence electrons, and it loses them to complete its outer shell.
Teachers call it "one fact, fully handled" — exactly what this page does for Erbium. The answer sits at the top in bold; scroll for the working, the shell-by-shell breakdown and the two questions students ask most. Need the whole picture instead — history, characteristics, uses, exam questions? The full Erbium page is one click away.
Counting the valence electrons
From the configuration [Xe] 4f^12 6s^2, Erbium'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: Erbium belongs to the f-block of the periodic table, period 6.
Valency vs valence electrons
Valence electrons are what you count (2 for Erbium); 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 Erbium from its group?
As an f-block element Erbium is not assigned a group; examiners accept its common valency of 3.
Why does Erbium show a fixed valency?
Erbium has 2 valence electrons and reaches a complete outer shell in one consistent way, so its valency stays fixed at 3.