Question

How many pi bonds are in `CO_2`?

Answer 1

2 `pi` bonds

Let's consider the lewis structure of `CO_2`, and we can consult our molecular orbital manifold between the bonding species if need be.

Explanation:

For `CO_2` we have:

We know that `sigma` bonds form for single bonds (including dative bonds), and that the `pi` bonds will be all of the bonds which form thereafter.

Counting the bonds within the species, I see two `pi` bond, and two `sigma` bond.

Let's place the electron between the bonding oxygen and central atom carbon in our molecular orbital manifold:

Notice how the electron from both species, distributed into the manifold are colored red - can you count the number of `pi` bond that are present within the manifold? I see one `pi` bond within the manifold - and the manifold is done for exactly half of the symmetrical species. So, noting that the other half of the species will follow the same configuration - we can deduce that there are 2 `pi` bond in the `CO_2` species.