What is the excited state of carbon?

The ground state of carbon is ##"1""s"^"2""2s"^"2"2"""p""^2##. An excited state electron configuration of carbon is ##"1""s"^"2""2s"^1"2p"^3"##. This is the state of carbon when it undergoes chemical to form four covalent bonds, as in methane, ##"CH"_"4"##. However, the experimental evidence shows that all four bonds have the same energy, which can only be explained by the concept that the 2s and 2p orbitals hybridize to form four ##"sp"^3## orbitals, each with one unpaired electron.