Why are most molecules in the singlet state instead of the triplet state?

[hariharan venkatasu]

Most molecules are in singlet ground state which is of higher energy than triplet lower energy state .According to thermodynamics molecule tend to remain in lower energy state.Therefore,I presume molecules should remain in triplet state .Could anyone clarify my point

 

[mjc123]

Most molecules do not have a "lower energy triplet state". For most molecules, the ground state is a singlet, in which all the electrons are paired. An exception is dioxygen, which has two degenerate antibonding orbitals and two electrons to go in them. In this case, the ground state is the triplet (one electron in each orbital, with parallel spins). Molecules with unpaired electrons tend to be reactive, which is why most stable molecules have all-paired electrons.

 

[hariharan venkatasu]

Thank you very much for your reply .Let me know why the ground state is singlet?

 

[hariharan venkatasu]

Further to my last post , you have mentioned that molecules with unpaired electrons tend to to be reactive. That means triplet state molecules to be highly reactive .Then oxygen in triplet ground state should be reactive .This is not the case .Could you please clarify this point?

 

[PeterDonis]

oxygen in triplet ground state should be reactive .This is not the case

Yes, it is. Oxygen is one of the most reactive molecules there is. We call such reactions "combustion" and they typically release a lot of energy.