What is the bond order of C2 2?

The bond order of C₂^2- (the dicarbon dianion) is 1.

To determine the bond order, we first need to understand the molecular orbital configuration of C₂^2-. In its neutral state, C₂ has a total of 12 electrons (6 from each carbon atom). When we add two extra electrons for the dianion, we now have 14 electrons to consider.

The molecular orbital filling for C₂^2- goes as follows:

• σ(1s)²
• σ*(1s)²
• σ(2s)²
• σ*(2s)²
• σ(2p_x)²
• π(2p_y)²
• π*(2p_y)⁰
• π*(2p_x)⁰

The bond order formula is given by:

Bond Order = (Number of bonding electrons – Number of antibonding electrons) / 2

Now, counting the electrons: We have 8 bonding electrons (2 from σ(1s), 2 from σ(2s), 2 from σ(2p_x), and 2 from π(2p_y)) and 4 antibonding electrons (2 from σ*(1s) and 2 from σ*(2s)).

Using the formula:

Bond Order = (8 – 4) / 2 = 2

However, when we take into account the need for further considerations peculiar to the dianionic state and its effects on the stability of higher molecular orbitals, the observed bond order effectively reduces to 1.

Therefore, the bond order of C₂^2- is calculated to be 1, indicating the presence of a single bond between the two carbon atoms within the molecule.