Question

`CO_(2)` is a linear, monomeric covalent compound. Its real structure is a resonance hybrid of _____resonance structures.
A. two
B. four
C. three
D. it does not exhibit resonance

Answer 1

Correct Answer - C
`CO_(2)` molecule is mostly described as
`:overset(..)(O)=C=overset(..)(O):`
This structure predicts that `CO_(2)` is linear and both `C-O` bonds should have the same length `(122 p m)`. Experimentally, both `C-O` bonds are found to be `115` pm indicating some triple bond character. This can be justified if `CO_(2)` is considered to be a resonance hybrid of three resonance forms:
`overset(-):overset(..)underset(..)(O)-C-=O:^(+) harr :overset(..)(O)=C=overset(..)(O):harr:overset(+)(O)-=C-underset(..)overset(..)Ooverset(-):`
In addition to `sigma` bonds between `C` and `O`, there is a three-center four-electron `pi` bond covering all three atoms.