Question

Which of the following order are correct with respect to the strength of XX single $\sigma$ covalent bonds?
(p) $Si-Si<Ge-Ge$ (q) $N-N<P-P$ (r) $Cl-Cl>F-F$ (s) $O-O<S-S$

• A. (p), (q) and (r) only
• B. (q), (r) and (s) only
• C. (q) and (s) only
• D. (p), (q), (r) and (s)

Answer 1

Answer: (B)

(q), (r) and (s) only

Higher is the bond dissociation energy, higher is the bond strength.
$Si-Si=222$ kJ mol${}^1$ ; $Ge-Ge=188$ kJ mol${}^1$
$N-N=165$ kJ mol${}^1$; $P-P=200$ kJ mol${}^1$
$Cl-Cl=239$ kJ mol${}^1$, $F-F=159$ kJ mol${}^1$
$O-O=142$ kJ mol${}^1$, $S-S=263$ kJ mol${}^1$
Thus, the orders (q), (r) and (s) only are correct with respect to the strength of $X-X$ single $\sigma$ covalent bonds.