Bond order or C2-

To determine the bond order of C2-, you first need to draw the molecular orbital diagram for C2-.

In the molecular orbital diagram, two carbon atoms are connected by a double bond. Each carbon atom contributes two valence electrons, resulting in a total of four electrons to distribute.

The molecular orbital diagram for C2- would look like this:

Sigma 2p(pi) antibonding (σ*2p(pi)) - Empty
Sigma 2p(pi) bonding (σ2p(pi)) - Filled
Pi 2p(y) (π2p(y)) - Filled
Pi 2p(x) (π2p(x)) - Filled
Sigma 2p(sigma) antibonding (σ*2p(sigma)) - Empty
Sigma 2p(sigma) bonding (σ2p(sigma)) - Filled

The bond order is calculated by subtracting the number of electrons in the antibonding orbitals from the number of electrons in the bonding orbitals and then dividing by 2.

In the case of C2-, there are 2 electrons in bonding orbitals (σ2p(pi), π2p(y), π2p(x)), and 2 electrons in antibonding orbitals (σ*2p(sigma)).

Therefore, the bond order of C2- is:

(2 - 2) / 2 = 0

The bond order of C2- is 0, indicating that it is not a stable molecule.