The electrochemical behaviour of aromatic organo-element compounds bearing a substituent (involving S, Se, Te atoms with lone pair or/and a bonding orbital like α-C-Si) with its own important contribution to the HOMO has been studied. The reactivity of the organic species in the electrochemical reactions is mainly determined by a set of fundamental parameters of the chemical structure (energies of frontier MO, D_RX) which govern not only the type of electron transfer, but also the nature of the potential-determining reaction of the ion-radical intermediates in a stepwise processes. The ensuing reactivity of the ion radicals is determined by the sum of the electronic and stereoelectronic effects, affecting the charge localisation in the ion radical. A compensation of the charge and a lowering of the energy of the ion radicals promote the latter to reveal their radical properties (dimerisation, disproportionation) rather than their ionic ones. Using established peculiarities of the chemical structure/electrochemical reactivity relationship, a number of processes of functionalization and electrosynthesis of organo-element compounds have been realised.