Question

Select the correct statement about carbonium ion, $CH_5^ +$
A. This cation shares eight electrons among five bonds
B. There is no empty orbital
C. It is not electron deficient
D. All the above are correct statements

Answer 1

The carbonium ion $CH_5^ +$is a fine example of a 3 centre- 2 electron species in which there bond pairs between the carbon and hydrogen atom have 6 electrons among themselves but the remaining two $C - H$ bonds have only two electrons among themselves.

Complete step by step answer:

A carbon atom has a total of four electrons in its valence shell and thus, is a tetravalent atom.
The electronic configuration of carbon atom is = $1{s^2}2{s^2}2{p^2}$
The reaction that takes place during the formation of the corresponding carbocation is:
$C{H_4} + {H^ + } \to CH_5^ +$
It acts as an ambident atom as it can either gain four electrons or lose four electrons to attain its octet and thus, gain complete stability. Now, in the carbonium ion mentioned above, there is an additional hydrogen atom attached to the carbon atom and thus, we can find that the carbocation has 3 normal $C - H$ bond pairs and the remaining two electrons circulate between the remaining two $C - H$ bond pairs. Now let us look at each option one by one with proper explanation.
A. There are five bind pairs in the carbonium ion. The three $C - H$ bond pairs are normal and the remaining two bond pairs are formed by a $3C - 2{e^ - }$ bond. Thus, this cation shares eight electrons among five bonds.
B. As the octet is complete for the carbon atom, there is no empty orbital present.
C. The carbocation is an electron rich species although it has positive charge over it as all the orbitals are completely filled in it. Hence, this species is not electron deficient.
Thus, the correct option is D. All the above are correct statements.

Note:
A three centered two electron bond is a special case of bonding between atoms. It is such a chemical bond which is formed when two electrons or a pair of electrons is mutually shared between three consecutive adjacent atoms in the space.