first-row transition series (Sc to Zn)

The first row of transition metals is the one full of household names: scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc. These ten elements, taken left to right, are where most of us meet transition-metal chemistry — the iron in steel and blood, the chromium in shiny plating, the copper in wires, the nickel and cobalt in batteries. Reading across them as a series reveals how the properties change in an orderly way as we add electrons one at a time.

What is happening across the row is the gradual filling of the 3d subshell. Each step right adds one proton and (broadly) one 3d electron. Because that added electron goes into an inner-lying d orbital while the outer 4s shell stays roughly the same, the atoms change only slowly: their sizes barely shrink across the row, unlike the dramatic contraction seen in main-group rows. The highest oxidation state rises through the early elements as more electrons become available to lose (titanium reaches +4, vanadium +5, chromium +6, manganese +7), then falls away in the later metals where the d electrons sit too tightly to remove, so iron, cobalt, nickel and copper are dominated by +2 and +3. Two small bumps spoil the perfectly smooth march: chromium is 3d5 4s1 and copper is 3d10 4s1, because a half-filled or completely full d shell is a touch more stable, so each borrows one electron from the 4s.

Knowing the trends across this row is the practical core of transition-metal chemistry, because these are the metals of industry and life. The descriptive chemistry of chromium, manganese, iron, cobalt, nickel and copper — their oxides, halides and watery ions — is treated metal-by-metal elsewhere in this field; here the point is that they form a connected family whose behavior shifts smoothly and predictably as the 3d shell fills.