Question

How many pi bonds can the atom form?

Answer 1

Assuming the discussion is restricted to organic chemistry and we are talking about carbon, two pi bonds are possible.

Explanation:

Consider the triple bond in Ethyne

Carbon has four valence electrons so in order to make 4 bonds, it must hybridize its orbitals to make that possible. In this case, Carbon takes on an `sp` hybrid configuration in which one electron goes into each `sp` hybrid orbital and the other two each go into the unhybridized `p` orbitals.

The electrons in each carbon's `sp` orbital that face one another participate in a tight sigma bond. The electrons in the unhybridized `p` orbitals form a pi bond like a bridge.

Consider also `CO_2`

Carbon has the same `sp` hybridization here where the two `sp` orbitals participate in sigma bonds with the oxygen while each unhybridized `p` orbital forms a double bond with the adjacent oxygen.

While a quadruple bond is possible for coordination compounds with transition metals, here is no hybridization scheme that allows for a quadruple bond to form between two atoms in organic chemistry.