Chapter 19: The d-Block Elements

Early d-block metals such as titanium, chromium, manganese, and iron are typically extracted from oxide ores through reduction processes, while later members like cobalt, nickel, copper, and zinc occur as sulfides or arsenides and require roasting followed by electrolytic refining. The platinum group metals and coinage metals exhibit distinct recovery pathways reflecting their scarcity and nobility. Physical properties across the d-block are understood through band theory and metallic bonding models, with maximum hardness and melting points occurring around group six elements and declining toward group twelve. The lanthanide contraction explains unexpected trends in the fifth d-series, particularly affecting heavier metals like hafnium, tantalum, and tungsten. Chemical properties reveal systematic variation in oxidation states: early transition metals achieve high oxidation numbers such as manganese in the heptavalent state and chromium in the hexavalent state, while later members predominantly stabilize lower oxidation states, particularly the divalent and trivalent forms. High oxidation state species function as powerful oxidizing agents, exemplified by permanganate and chromate ions. Descending a group increases both the stability of maximum oxidation states and coordination flexibility in heavier congeners. Noble character, most evident in silver, gold, and platinum group elements, accounts for their resistance to corrosion and their applications in catalysis and jewelry. The chapter systematically covers binary compounds including halides ranging from ionic dihalides to covalent polyhalides, oxides spanning from simple ionic monoxides to volatile molecular oxides, and sulfides with diverse structural types from layered disulfides to discrete pyrite-structure compounds. Oxido complexes and polyoxometallate anions demonstrate extensive condensation phenomena and reversible redox chemistry essential to materials science. Metal-sulfur clusters and thiometallates connect to bioinorganic mechanisms in enzymes. Nitrido and alkylidyne complexes showcase multiple bonding interactions with nitrogen and carbon ligands at elevated oxidation states. Metal-metal bonded species from quadruple-bonded dimers to extended clusters illustrate how direct metal-metal interactions determine structural geometry and electronic properties throughout the d-block.