# Molecular antibonding orbitals energy

When we heat hydrogen the energy of the molecular orbital of H2(1s) is increased .What happens to the energy of the antibonding molecular energy of hydrogen(1s*)?

• So is it possible to stabilize an HeH molecule in high temperatures where the 1s* and 2s molecular orbitals will overlap? – Jelly Strawberry Mar 30 at 23:49
• Most likely no because you have an odd number of electrons and large nuclear repulsion. HeH(+) can be made and is very unstable. However what is helpful here is the even number of electrons, also remember that the orbitals will couple and mix to form new bonding and antibonding pairs. – Cody Aldaz Mar 31 at 0:03
• The molecular orbitals themselves are not changed on heating, but more of the vibrational and rotational energy levels within the ground state potential-well become populated. Eventually there will be enough vib/rot energy to dissociate the molecule. Excited states can have a potential well also (and so behave like the ground state) but others are also repulsive in which case there are no vibrational/rotational levels. The way to excite an excited state is by absorbing a photon as they are usually too high in energy to be reached thermally, e.g. by collisions. – porphyrin Mar 31 at 7:23

## 1 Answer

Energy is not stored in the energy levels themselves but in the states which occupy them. At normal room temperature the bonding orbitals are occupied according to Maxwell-Boltzmann's statistics $$P_i =e^{\epsilon_i /kT}/Z$$, and store that chemical energy. At higher temperatures the antibonding orbital will become occupied releasing the chemical energy.

• Yes but in hydrogen ground state 1s is filled and 1s* doesn't have any electron. – Jelly Strawberry Mar 30 at 23:38
• "Energy is not stored in the energy levels themselves but in the states which occupy them." very well worded! – user1271772 Mar 31 at 15:38