Valency of Samarium (Sm)
Samarium shows variable valency — most commonly 2 and 3 — because it is a f-block element whose outer electrons can join bonding in more than one way.
Teachers call it "one fact, fully handled" — exactly what this page does for Samarium. 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 Samarium page is one click away.
Counting the valence electrons
From the configuration [Xe] 4f^6 6s^2, Samarium'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: Samarium belongs to the f-block of the periodic table, period 6.
Why Samarium has more than one valency
The common valencies are 2 and 3. Both the outer s electrons and the nearby (n−1)d electrons sit close in energy, so Samarium can offer different numbers of them in different compounds — giving ions such as Sm²⁺ and Sm³⁺ and families of compounds like SmX / Sm₃X₂.
Valency vs valence electrons
Valence electrons are what you count (2 for Samarium); valency is what the atom will do to complete its outer shell (2 and 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 Samarium from its group?
As an f-block element Samarium is not assigned a group; examiners accept its common valency of 2 and 3.
Why does Samarium show variable valency?
Because both its outer shell and the nearby inner subshell can participate in bonding, Samarium forms more than one stable ion — hence valencies 2 and 3.