( ( When ( you ( ( add ( ( ( an electron ) and ) ( a proton ) ) ) ( to hydrogen ) ) ) ) ( it ( ( becomes ( ( ( ( ( helium , ) ( number 2 ) ) , ) and ) ( ( another gas ) ( at ( room temperature ) ) ) ) ) . ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (PRP you)) (VP (VBP add) (NP (NP (DT an) (NN electron)) (CC and) (NP (DT a) (NN proton))) (PP (TO to) (NP (NN hydrogen)))))) (NP (PRP it)) (VP (VBZ becomes) (NP (NP (NNP helium)) (, ,) (NP (NN number) (CD 2)) (, ,) (CC and) (NP (NP (DT another) (NN gas)) (PP (IN at) (NP (NN room) (NN temperature)))))) (. .)))
When you add an electron and a proton to hydrogen it becomes helium, number 2, and another gas at room temperature.
(ROOT (S (NP (NNP Hydrogen)) (VP (VBZ is) (PP (IN in) (NP (NP (NN gas) (NN form)) (PP (IN at) (NP (NN room) (NN temperature)))))) (. .)))