Chemistry · Ch 9 — Elements of Group 13, 14 and 15
Catenation
Catenation
Catenation is the property by which atoms of the same element link to one another through covalent bonds to form chains and rings. How strongly an element catenates depends on the strength of the bond it forms with itself: among the group 14 elements, carbon shows by far the greatest tendency to catenate because the C-C single bond (348 kJ/mol) is unusually strong, with a C-C bond distance in such chains of 154 pm. The catenation tendency falls sharply down the group, following the order C >> Si > Ge = Sn, and this fall tracks the bond enthalpies directly: Si-Si is 297 kJ/mol, Ge-Ge is 260 kJ/mol and Sn-Sn is only 240 kJ/mol (see the bond-enthalpy table against this section). Lead shows essentially no catenation at all, consistent with its very weak Pb-Pb bond and …
C-C bond enthalpy 348 kJ/mol. Si-Si bond enthalpy 297 kJ/mol. Ge-Ge bond enthalpy 260 kJ/mol. Sn-Sn bond enthalpy 240 kJ/mol. The steady fall in bond enthalpy down the group tracks directly with the steadily weakening catenation tendency C >> Si > Ge = Sn (with Pb showing essentially no catenation), confirming that E-E bond strength is the main fact …