Question

Which of the following elements forms double or triple bonds involving p-p bonding?
A. Carbon
B. Silicon
C. Germanium
D. Tin

Answer 1

Hint: We should know that the p-p bonding is formed by the p-orbital’s electrons only. So, here we have to look through each option what type of orbitals they have in their outermost shell. By knowing the electronic configuration, we can know what type of orbitals they have.

Complete answer:
To solve such a problem, first of all we must have the knowledge about what type of electronic configuration the elements are having. The elements having only p-orbitals will have a condition where one half-filled p-orbital from each contributing atom will undergo a head-on overlapping along the internuclear axis.
So, let us go through each option.
(a) The electronic configuration of carbon is $[He]2s^{2}2p^2$. And we can see that the element has no d-orbitals. Due to absence of d-orbitals, the bonding (whether it is double or triple bonding) will take place through p-p back bonding.
(b) The electronic configuration of silicon is $[He]2s^{2}2p^{6}3s^{2}3p^2$. And we know that there is a vacant d-orbital. So, due to the presence of vacant d-orbital, the multiple bonding (whether it is double or triple) takes place involving d-p multiple bonding.
In option (c) and (d) Germanium and tin are higher group elements with electronic configuration $[Ar]3d^{10}4s^{2}4p^2$ and $[Kr]4d^{10}5s^{2}5p^2$ will have d-p overlapping while formation of double and triple bonds.

Hence, the correct option is A.

Note:
A double bond generally consists of one sigma bond and one pi bond while a triple bond consists of two pi bonds and one sigma bonds. Single bonds are always formed of sigma bonds. It should be noted that the lateral overlap of p-orbitals will result in formation of pi bonds. And on moving down the group, size of the orbital increases and the extent of pi-bond formation decreases.