Question

The element that does not show catenation is

• A. Ge
• B. Sn
• C. Si
• D. Pb

Answer 1

The correct option is D Pb

The property of self-linking of atoms of an element through covalent bonds to form straight or branched chains and rings of different sizes is called catenation. Down the group, catenation tendency decreses due to decrese in element bond strength. Carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb) are group- 14 elements.
Catenation tendency is highest in carbon while silicon has second highest tendency of catenation among all elements of family due to higher bond energy. The decreasing tendency of catenation among group 14 elements is as follows:
$C>>Si>Ge\approx Sn$
However, Pb does not show catenation.
THEORY
Catenation:

• Carbon atoms have the tendency to link with one another through covalent bonds to form chains and rings.
• Bond enthalpy (in $kJmo{l}^{1-}$) of bond C-C, Si-Si, Ge-Ge, Sn-Sn are 348, 297, 260, 240 respectively.
• Down the group, the size increases, tendency to show catenation decreases.
• The order of catenation is $C>>Si>Ge\approx Sn$.
• Lead does not show catenation
• Due to the property of catenation and p𝜋-p𝜋 bond formation, carbon is able to show allotropic forms.
• Allotropic forms of C are crystalline and amorphous.
• Diamond and graphite are two well-known crystalline forms of carbon. The third form of carbon known as fullerenes was discovered by H.W. Kroto, E Smalley, and R.F. Curl in 1985.