( So ( , ( ( if ( ( an atom ) ( had ( six protons ) ) ) ) ( , ( it ( ( ( should also ) ( have ( six electrons ) ) ) . ) ) ) ) ) )
(ROOT (S (IN So) (, ,) (SBAR (IN if) (S (NP (DT an) (NN atom)) (VP (VBD had) (NP (CD six) (NNS protons))))) (, ,) (NP (PRP it)) (VP (MD should) (ADVP (RB also)) (VP (VB have) (NP (CD six) (NNS electrons)))) (. .)))
So, if an atom had six protons, it should also have six electrons.
(ROOT (S (NP (NNP Carbon) (NNS atoms)) (VP (VBP have) (NP (NP (CD six) (NNS protons)) (CC and) (NP (NP (NNS electrons)) (NP (DT each))))) (. .)))