Physical properties

Table 1.1 lists selected physical properties of the group 14 elements. A comparison with Table 12.1 shows there to be some similarities in trends down groups 13 and 14. Ionization energies and cation formation On descending group 14, the trends in ionization energies reveal two particular points:

• the relatively large increases between values of IE₂ and IE₃ for each element;
• the discontinuities (i.e. increases) in the trends of values of IE₃ and IE₄ at Ge and Pb.

  The sums of the first four ionization energies for any element suggest that it is unlikely that M⁴⁺‏ ions are formed. For example, although both SnF₄ and PbF₄ are non-volatile solids, neither has a symmetrical lattice structure in the solid state. Both SnO₂ and PbO₂ adopt the rutile lattice, but the fact that PbO₂ is brown argues against a formulation of Pb⁴⁺‏(O^2-)₂. Agreement between values of lattice energies determined using a Born–Haber cycle and calculated from an electrostatic model is good for SnO₂, but is poor for PbO₂. Thus, values of the M⁴⁺‏ ionic radii (Table 1.1) should be treated with some caution.

Table 1.1 Some physical properties of the group 14 elements, M, and their ions.

Aqueous solution chemistry involving cations of the group 14 elements is restricted mainly to Sn and Pb , and so Table 1.1 gives E^o values only for these metals.