( ( If ( it ( ( were not ) ( for ( ( ( the spin ) ( -LRB- ( ( the ( ` ( ( ( ( up ' ) or ) ` ) ( ( down ' ) flavor ) ) ) ) -RRB- ) ) ) ( of ( the electron ) ) ) ) ) ) ) ( , ( ( many ( electron atoms ) ) ( ( would ( be ( filled ( by ( ( ( ( putting ( one electron ) ) ( in ( each ( hydrogen-like orbital ) ) ) ) , ) ( to ( satisfy ( the ( Pauli ( exculsion principle ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN If) (S (NP (PRP it)) (VP (VBD were) (RB not) (PP (IN for) (NP (NP (NP (DT the) (NN spin)) (PRN (-LRB- -LRB-) (S (NP (DT the)) (NP (`` `) (NP (IN up)) ('' ') (CC or) (`` `) (NP (NP (NN down) (POS ')) (NN flavor)))) (-RRB- -RRB-))) (PP (IN of) (NP (DT the) (NN electron)))))))) (, ,) (NP (JJ many) (NN electron) (NNS atoms)) (VP (MD would) (VP (VB be) (VP (VBN filled) (PP (IN by) (S (VP (VBG putting) (NP (CD one) (NN electron)) (PP (IN in) (NP (DT each) (JJ hydrogen-like) (NN orbital))) (, ,) (S (VP (TO to) (VP (VB satisfy) (NP (DT the) (NNP Pauli) (NN exculsion) (NN principle))))))))))) (. .)))
If it were not for the spin (the 'up' or 'down' flavor) of the electron, many electron atoms would be filled by putting one electron in each hydrogen-like orbital, to satisfy the Pauli exculsion principle.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD one) (NNS electrons)) (PP (IN in) (NP (DT the) (NN hydrogen) (NN atom))))) (. .)))