The d- and f-Block Elements

The transition (d-block) and inner-transition (f-block) elements occupy the middle of the periodic table and are among the most useful elements we know — iron, copper, chromium, manganese, the platinum metals, and the lanthanoids and actinoids. This chapter, worth a reliable 6-8 Board marks and 2-3 JEE/NEET questions a year, explains why these elements share a family of characteristic properties: partially filled d (or f) subshells. We study their electronic configurations (including the famous exceptions of Cr, $3d^5 4s^1$, and Cu, $3d^{10} 4s^1$), the trends in atomic and ionic size, the high enthalpies of atomisation and irregular ionisation enthalpies, and the great variety of oxidation states. We see why most form coloured ions (d-d transitions), are paramagnetic (using the spin-only formula $\mu = \sqrt{n(n+2)}$ BM), act as catalysts, and form complex, interstitial and alloy compounds. We examine two key compounds in detail — potassium dichromate ($\text{K}_2\text{Cr}_2\text{O}_7$) and potassium permanganate ($\text{KMnO}_4$) — and finish with the f-block: the lanthanoids (and the all-important lanthanoid contraction) and the actinoids. Every trend, every reaction, and every exam-favourite comparison is covered.