Transition metal — স্থানান্তর ধাতু
Transition metals are the d-block metals of Groups 3–12: hard, useful, colourful and full of variable valency.
Definition
Transition metals occupy the d block, Groups 3 to 12, where the inner d subshell is filling. Iron, copper and gold all live here: hard, dense, high-melting metals. Two habits make them exam favourites: variable oxidation states, because their d electrons can join in, and brightly coloured compounds, like the blue of copper sulfate solution or the pale green of iron(II) salts. Many also catalyse — iron speeds ammonia making, vanadium oxide runs sulfuric acid plants. Steel, brass and bronze, civilization's backbone, are transition metal chemistry.
For example
The Padma Bridge stands on steel — mostly iron with a pinch of carbon — while copper from the same d block carries the electricity to your charging point.