Question

Which of the following is/are correct for group 14 elements-

• A. The stability of dihalides are in the order $C{X}_2<Si{X}_2<Ge{X}_2<Sn{X}_2<Pb{X}_2$
• B. The ability to form $p\pi -p\pi$ multiple bonds among themselves increases down the group
• C. The tendency for catenation decreases down the group
• D. They all form oxides with the formula $M{O}_2$

Answer 1

Answer: (A), (C), (D)

The correct options are
A The stability of dihalides are in the order $C{X}_2<Si{X}_2<Ge{X}_2<Sn{X}_2<Pb{X}_2$
C The tendency for catenation decreases down the group
D They all form oxides with the formula $M{O}_2$

$\left(A\right)$ Carbon and silicon do not form any stable dihalides as germanium, tin or lead. This is because covalent bonds decrease in strength with increasing atomic size and the ionization energies for the heavier elements of the group are higher than expected due to a higher $Z_{eff}$, the relative stability of the $+2$ oxidation state increases smoothly from carbon to lead.

$\left(B\right)$ The ability to form $p\pi -p\pi$ multiple bonds among themselves decreases down the group. This type of $\pi$ bonding is not strong for the heavier p-block elements.

$\left(C\right)$ The tendency to catenate (to form chains of like atoms) decreases rapidly as we go down group 14 because bond energies for both the E–E and E–H bonds decrease with increasing atomic number. As a result of this trend, the thermal stability of catenated compounds decreases rapidly from carbon to lead.

$\left(D\right)$ Carbon forms $CO$ and $C{O}_2$ while other elements form $M{O}_2$ except lead which forms $PbO$ oxide.