( It ( ( was ( ( ( discovered ( -LRB- ( ( along ( with ( ( krypton and ) xenon ) ) ) -RRB- ) ) ) ( in 1898 ) ) ( as ( one ( of ( ( the ( three ( residual ( rare ( inert elements ) ) ) ) ) ( ( ( remaining ( in ( dry air ) ) ) , ) ( after ( ( nitrogen ( , ( oxygen ( , ( argon ( and ( carbon dioxide ) ) ) ) ) ) ) ( are removed ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBD was) (VP (VBN discovered) (PRN (-LRB- -LRB-) (PP (RB along) (IN with) (VP (VB krypton) (CC and) (VB xenon))) (-RRB- -RRB-)) (PP (IN in) (NP (CD 1898))) (PP (IN as) (NP (NP (CD one)) (PP (IN of) (NP (NP (DT the) (CD three) (JJ residual) (JJ rare) (NN inert) (NNS elements)) (VP (VBG remaining) (PP (IN in) (NP (JJ dry) (NN air))) (, ,) (SBAR (IN after) (S (NP (NN nitrogen) (, ,) (NN oxygen) (, ,) (NN argon) (CC and) (NN carbon) (NN dioxide)) (VP (VBP are) (VP (VBN removed)))))))))))) (. .)))
It was discovered (along with krypton and xenon) in 1898 as one of the three residual rare inert elements remaining in dry air, after nitrogen, oxygen, argon and carbon dioxide are removed.
(ROOT (S (NP (NNP Nitrogen) (, ,) (NNP oxygen) (CC and) (NNP argon)) (VP (VBP are) (NP (NP (DT the) (CD three) (JJS most) (JJ common) (NNS elements)) (PP (IN in) (NP (NP (DT the) (NN air)) (SBAR (S (NP (PRP we)) (VP (VB breathe)))))))) (. .)))