Select the word or phrase that complete each sentence (const…

Select the word or phrase that complete each sentence (constitutional isomers, diastereomers, enantiomers, meso compounds, higher, lower, reaction, addition, carbocation, carbanion, nucleophile, electrophile, elimination, heterolysis, homolysis, reagent, substitution, stronger, weaker, charge, concerted, two step, SN1, SN2, racemization, hyperconjugation, alkyl halides, inversion):     A …………………………. is a sp2 hybridized and trigonal planar and contains a vacant p orbital.  Complete word/phrase and correct spelling (verbatim) is required. No partial credit.