Which of the following statements relating to molecular orbital (mo) theory is incorrect? a. combination of two 2p orbitals may result in either latex: \sigma σ or latex: \pi π mos. b. combination of two atomic orbitals produces one bonding and one antibonding mo. c. a bonding mo is lower in energy than the two atomic orbitals from which it is formed. d. in a stable molecule having an even number of electrons, all electrons must be paired. e. a species with a bond order of zero will not be stable.

d. In a stable molecule having an even number of electrons, all electrons must be paired.

Explanation:

Which of the following statements relating to molecular orbital (MO) theory is incorrect?

a. Combination of two 2p orbitals may result in either σ or π MOs. TRUE. If the atomic orbitals overlap frontally, a σ MO is produced while if the atomic orbitals overlap laterally, a π MO is produced.

b. Combination of two atomic orbitals produces one bonding and one antibonding MO. TRUE. The bonding MO has less energy than the antibonding MO.

c. A bonding MO is lower in energy than the two atomic orbitals from which it is formed. TRUE. The bonding MO is more stable than the individual atomic orbitals.

d. In a stable molecule having an even number of electrons, all electrons must be paired.  FALSE. Let's consider, for example, the molecular orbitals of O₂:

The electrons in the degenerated π* orbitals are not paired.

e. A species with a bond order of zero will not be stable. TRUE. For a species to be stable, the bond order must be higher than zero.

it is the minimum amount of material needed to sustain a fission reaction.

critical mass is the minimum amount of fissionable material that must be assembled for a sustained fission reaction to take place. although two to three neutrons are produced for every fission, not all of these neutrons are available for continuing the fission reaction. if the conditions are such that the neutrons are lost at a faster rate than they are formed by fission, the chain reaction will not be self-sustaining.   at the point where the chain reaction can become self-sustaining, this is referred to as critical mass.