Question

Which of the following contains only three pairs of electrons?

• A. Free radical
• B. Carbanion
• C. Carbocation
• D. All of these

Answer 1

The correct option is C

Carbocation

The explanation for the correct answer:

(C) Carbocation

• A carbocation is a carbon atom having a positive charge and three bonds.
• It is also known as carbonium ion.
• Carbocation is an even-electron cation that has a positive charge on the carbon atom.
• Carbocations have six electrons in their valence shell making them electron deficient.
• They are unstable electrophiles and react very with nucleophiles.
• Therefore, carbocation has three pairs of electrons and it is the correct answer.

The explanation for the incorrect options:

(A) Free radical

• A free radical is an atom or molecule containing one or more unpaired electrons in the valence shell.
• It is capable of independent existence.
• Free radicals are very unstable and short-lived.
• Therefore, it does not have three pairs of electrons and is the incorrect answer.

(B) Carbanion

• A carbanion is a negatively charged ion in which a carbon atom has three bonds.
• It has a formal negative charge whose value is at least -1.
• In carbanion, one pair of electrons on carbon is not bonded and the other six electrons are bonded to other atoms.
• So carbanion has eight electrons.
• Therefore, it does not have three pairs of electrons and is the incorrect answer.

(D) All of these

• Free radical and carbanion do not have three pairs of electrons and is the incorrect answer.
• Therefore, option (D) is incorrect.

Hence, the correct option is (C) Carbocation.