( ( ( Hydrogen atoms ) ( ( can easily ) ( ( enter ( ( ( ( most metallic ) solids ) and ) even ) ) ( at ( ( ( very small ) concentrations ) ( -- ( ( ( ( as ( little ( as one ) ) ) proton ) ( per ( million ( metal atoms ) ) ) ) -- ) ) ) ) ) ) ) ( they ( ( make ( ( the metal ) ( too ( brittle ( for ( engineering use ) ) ) ) ) ) . ) ) )
(ROOT (S (S (NP (NN Hydrogen) (NNS atoms)) (VP (MD can) (ADVP (RB easily)) (VP (VB enter) (NP (NP (ADJP (RBS most) (JJ metallic)) (NNS solids)) (CC and) (RB even)) (PP (IN at) (NP (NP (ADJP (RB very) (JJ small)) (NNS concentrations)) (PRN (: --) (NP (NP (QP (RB as) (JJ little) (IN as) (CD one)) (NN proton)) (PP (IN per) (NP (CD million) (NN metal) (NNS atoms)))) (: --))))))) (NP (PRP they)) (VP (VBP make) (S (NP (DT the) (NN metal)) (ADJP (RB too) (JJ brittle) (PP (IN for) (NP (NN engineering) (NN use)))))) (. .)))
Hydrogen atoms can easily enter most metallic solids and even at very small concentrations--as little as one proton per million metal atoms--they make the metal too brittle for engineering use.
(ROOT (S (NP (JJ Metallic) (NNS solids)) (VP (VBP are) (VP (VBN composed) (ADVP (RB entirely)) (PP (IN of) (NP (JJ metallic) (NNS atoms))))) (. .)))