( ( ( Describe ( periods ( , ( ( groups and ) families ) ) ) ) ( on ( the ( periodic table ) ) ) ) . )
(ROOT (S (VP (VB Describe) (NP (NNS periods) (, ,) (NNS groups) (CC and) (NNS families)) (PP (IN on) (NP (DT the) (JJ periodic) (NN table)))) (. .)))
Describe periods, groups and families on the periodic 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)))) (. .)))