( ( The ( main ( group elements ) ) ) ( ( ( include ( ( ( ( ( groups 1 ) and ) 2 ) ( -LRB- ( ( excluding Hydrogen ) -RRB- ) ) ) ( on ( the ( ( left ( of ( ( ( the ( periodic table ) ) and ) groups ) ) ) ( ( 13 to ) 18 ) ) ) ) ) ) ( on ( ( the right ) ( of ( the table ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ main) (NN group) (NNS elements)) (VP (VBP include) (NP (NP (NNS groups) (CD 1) (CC and) (CD 2)) (PRN (-LRB- -LRB-) (PP (VBG excluding) (NP (NNP Hydrogen))) (-RRB- -RRB-)) (PP (IN on) (NP (DT the) (ADJP (VBN left) (PP (IN of) (NP (NP (DT the) (JJ periodic) (NN table)) (CC and) (NP (NNS groups))))) (QP (CD 13) (TO to) (CD 18))))) (PP (IN on) (NP (NP (DT the) (NN right)) (PP (IN of) (NP (DT the) (NN table)))))) (. .)))
The main group elements include groups 1 and 2 (excluding Hydrogen) on the left of the periodic table and groups 13  to 18 on the right of the table.
(ROOT (S (NP (NP (NNP Group) (CD 13)) (PP (IN of) (NP (DT the) (JJ periodic) (NN table)))) (VP (VBZ is) (ADVP (RB also)) (VP (VBN called) (NP (DT the) (DT the) (NN boron) (NN group)))) (. .)))