D And F Block Elements Class 12 One Shot 🔥 | All Concepts + NCERT + PYQs | Chemistry Chapter 4

Summary

Key Points

• —D-block elements, known as transition elements, are characterized by partially filled d-orbitals in their ground or common ionic states, acting as a bridge between electropositive S-block and electronegative P-block elements. 0:00
• —Transition metals exhibit variable oxidation states due to the participation of both ns and (n-1)d electrons in bonding, as their energy levels are very close. 20:00
• —The stability of half-filled (d⁵, f⁷) and fully-filled (d¹⁰, f¹⁴, f⁰) electronic configurations significantly influences the atomic radii, melting points, and reduction potentials of transition elements. 40:43
• —Lanthanoid contraction, caused by the poor shielding effect of 4f electrons, leads to a gradual decrease in atomic and ionic radii across the lanthanoid series, making 4d and 5d series elements exhibit similar sizes. 60:24
• —Transition metals form colored compounds due to d-d electronic transitions, where electrons absorb specific wavelengths of light and emit complementary colors. 79:45
• —D-block elements act as effective catalysts due to their variable oxidation states and the availability of empty d-orbitals, which facilitate bond formation with reactant molecules. 100:17
• —Important compounds like potassium dichromate (K₂Cr₂O₇) and potassium permanganate (KMnO₄) are strong oxidizing agents, with Cr(+6) and Mn(+7) being highly unstable and readily undergoing reduction. 120:02
• —Copper is an exception among transition metals, having a positive standard reduction potential, indicating its reluctance to oxidize and liberate hydrogen from acids under normal conditions. 140:01
• —F-block elements are divided into lanthanoids (4f series) and actinoids (5f series), both primarily exhibiting a stable +3 oxidation state, with actinoids showing a wider range of higher oxidation states and greater contraction due to poorer 5f shielding. 159:32
• —The formation of complex compounds by transition metals is attributed to their small size, high ionic charge, and the availability of vacant d-orbitals to accept electron pairs from ligands. 179:31