Valency of Osmium (Os)
Osmium shows variable valency — most commonly 4 and 6 — because it is a d-block element whose outer electrons can join bonding in more than one way.
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 Osmium page is one click away.
Counting the valence electrons
From the configuration [Xe] 4f^14 5d^6 6s^2, Osmium's outermost shell carries 2 electrons. For a d-block element the nearby inner "d" subshell can also lend electrons, which is where variable valency comes from.
Position check: Osmium belongs to group 8 of the periodic table, period 6.
Why Osmium has more than one valency
The common valencies are 4 and 6. Both the outer s electrons and the nearby (n−1)d electrons sit close in energy, so Osmium can offer different numbers of them in different compounds — giving ions such as Os⁴⁺ and Os⁶⁺ and families of compounds like Os₄X₂ / Os₆X₂.
Valency vs valence electrons
Valence electrons are what you count (2 for Osmium); valency is what the atom will do to complete its outer shell (4 and 6 here). Keep the two words straight and half the periodic-table chapter writes itself.
Students also ask
How do I find the valency of Osmium from its group?
Osmium sits in group 8; for this transition group the safe exam answer is its common valency, 4 and 6.
Why does Osmium show variable valency?
Because both its outer shell and the nearby inner subshell can participate in bonding, Osmium forms more than one stable ion — hence valencies 4 and 6.