Relativistic effects on the chemical bonding properties of the heavier elements and their compounds

It is now well established that the relativistic effects strongly influence the properties of the heavier ele-ments, specially the heavier elements of d- and f-block and also the heavier main group elements of s- and p -block. In fact, properties of the heavier elements are widely different from those of the theoretically predicted non-relativistic (NR) analogues. Several reviews on different aspects of the relativistic effects are available in very scattered forms. This review aims to make a comprehensive summary of all the known relativistic effects that influence the properties of the heavier elements like difference in elec-tronic configurations of the heavier d-block congeners; attainment of higher oxidation states by the heav-ier d-block congeners; special properties of gold and mercury; liquidity of mercury at room temperature (cf. Nr-Hg is solid); chemical inertness of the noble metals and mercury; linear coordination geometry of Au(I) and Ag(I); stability of the dimeric species Au2, Hg22', AuPt- and AuHg'; easy formation of amalgams with the noble metals but not with the other transition metals; stability of aurides (bearing Au-); yellow colour of gold (cf. NR-Au is white); colours of Bi(V) vs Sb(V) and Pb(IV) vs Sn(IV) compounds; lanthanide and actinide contraction; difference in the properties of lanthanides (Ln) and actinides (An): magnetic and spectral properties, bonding properties of 4f- and 5f-orbitals, bond length, hardness-softness, ligand selectivity, etc; the most reactive metal Cs (cesium) not Fr (francium) - apparently disobeying the peri-odic trend; inert pair effect; closed-shell supramolecular interactions like aurophilicity (i.e. metallophilic-ity) and halogen bonding (XB) by the heavier halogens; catalytic activity of platinum group metals (cf. NR-analogues inefficient catalysts); spin-orbit coupling in the heavier elements and heavy atom effect on NMR shift; structural preference (2D vs 3D) of gold nanoclusters; high voltage of lead-acid and mer-cury batteries (cf. NR-lead-acid battery cannot start our cars); etc.(c) 2022 Elsevier B.V. All rights reserved.