For a stable molecule the value of bond order must be

Options

A. zero
B. positive
C. negative
D. there is no relationship between stability and bond order.

Answer

B

Explanation

For stable molecule the value of bond order must be positive as bond order.
= (no. Bonding electrons) -(no. Of antibonding electrons)/(2)
The electrons in the bonding molecular orbital leads to lowering in energy and hence stability whereas in antibonding molecular orbital leads to destability.
(i) (-ve) bond order `Rightarrow` greater number of electrons in antibonding molecular orbital than bonding molecular orbital.Therefore molecule is less stable compared to the separated atoms.
0 bond order `rightarrow` number of bonding molecular orbital = number of antibonding molecular orbital.Therefore there is no gain in energyy in forming the molecule.
(+ve) bond order `rightarrow` number of electrons in bonding molecular orbital is more than those in antibonding molecular orbital.Therefore ther is a gain in enrgy while the bonding takes place.