( ( ( Carbon 's ) ( four valence ) ) ( ( ( electrons then ) ( half-fill ( each ( of ( the ( four orbitals ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Carbon) (POS 's)) (CD four) (NN valence)) (VP (VBZ electrons) (RB then) (VP (VB half-fill) (NP (NP (DT each)) (PP (IN of) (NP (DT the) (CD four) (NNS orbitals)))))) (. .)))
Carbon's four valence electrons then half-fill each of the four orbitals.
(ROOT (S (NP (NNP Carbon)) (VP (VBZ has) (NP (CD four) (JJ valence) (NNS electrons))) (. .)))