Final answer:
The bond order in Na2 is 0.5, indicating that the ion exists but is highly reactive.
Step-by-step explanation:
The molecular orbital theory can be applied to determine the bond order in Na2. First, we need to combine the two sodium valence atomic orbitals to produce bonding and antibonding molecular orbitals. Then, we can draw the molecular orbital energy-level diagram for this system. Next, we determine the total number of valence electrons in the Na2 ion. By filling the molecular orbitals in the energy-level diagram according to the Pauli principle and Hund's rule, we can find the bond order. In the case of Na2, the bond order is calculated as (2-1)/2=0.5. With a fractional bond order, we predict that the Na2 ion exists but is highly reactive.