Chemistry · Ch 4 — Transition and Inner Transition Elements
Position of d-block Elements in the Periodic Table
Position of d-block Elements in the Periodic Table
The transition metals occupy groups 3 to 12 of the modern periodic table, forming three complete horizontal series plus a partial, radioactive seventh-period series. The 3d series runs through the fourth period, from scandium to zinc (10 elements); the 4d series runs through the fifth period, from yttrium to cadmium (10 elements); and the 5d series runs through the sixth period, from lanthanum, then hafnium through to mercury (with the fourteen lanthanoids inserted between lanthanum and hafnium, discussed separately in section 4.5).
A subtlety arises with the group-12 elements -- zinc, cadmium and mercury. None of these three has a partially filled d-orbital, either in its elemental (metallic) state or in its normal (+2) oxidation state; each has a completely filled, stable d¹⁰ configuration. Strictly, this means they fail the IUPAC definition of a transition metal. Nonetheless, they are conventionally still treated and taught as transition elements, because their physical and chemical properties are essentially an extension of the properties of the true transition elements that precede them in their row -- they share similar densities, similar tendencies to form complexes, and similar catalytic uses, even though the d-orbital criterion is not technically met. …
What this figure shows. A full long-form periodic table with the four blocks colour-coded: the s-block (Groups 1-2, left edge) in one colour, the d-block (Groups 3-12, the broad central band running from Sc/Y/La-Hf down through Zn/Cd/Hg) in a second colour, the p-block (Groups 13-18, right side) in a third colour, and the f-block (the two 14-element rows of lanthanoids and actinoids, detached below the main body) in a fourth colour. The d-block visually forms the bridge connecting the highly reactive s-block metals on the left to the largely non-metallic p-block on the right, illustrating why transition-metal properti …