TeH 2+•• with ϕ D =148.9°. The increase in structural distortion of the diradical dications results from the steric effects arising from the larger covalent radius of the heavier chalcogens. The structure of the diradical dications and the position of spin-centers can help us predict the nature of magnetic exchange interactions. The spin alternation rule states that unpaired electrons on spin centers can polarize the spins on neighboring atoms, leading to an alternation of up and down spin densities between the two radical centers. Thus an odd number of atoms in the coupling pathway between the two spin centers can induce ferromagnetic coupling while an even number of atoms can lead to antiferromagnetic coupling.