( ( As ( ( the ( atomic number ) ) ( ( increases along ) ( ( each row ) ( of ( the ( periodic table ) ) ) ) ) ) ) ( , ( ( the ( additional electrons ) ) ( ( go ( into ( ( the ( same ( outermost ( principal ( energy level ) ) ) ) ) ( -LRB- ( ( also ( known ( as ( valence level ) ) ) ) -RRB- ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (DT the) (JJ atomic) (NN number)) (VP (VBZ increases) (PRT (RP along)) (NP (NP (DT each) (NN row)) (PP (IN of) (NP (DT the) (JJ periodic) (NN table))))))) (, ,) (NP (DT the) (JJ additional) (NNS electrons)) (VP (VBP go) (PP (IN into) (NP (NP (DT the) (JJ same) (JJ outermost) (JJ principal) (NN energy) (NN level)) (PRN (-LRB- -LRB-) (VP (ADVP (RB also)) (VBN known) (PP (IN as) (NP (JJ valence) (NN level)))) (-RRB- -RRB-))))) (. .)))
As the atomic number increases along each row of the periodic table, the additional electrons go into the same outermost principal energy level (also known as valence level).
(ROOT (S (NP (NP (NNS Electrons)) (PP (IN in) (NP (NP (DT the) (JJ outer) (NN energy) (NN level)) (PP (IN of) (NP (DT an) (NN atom)))))) (VP (VBP are) (VP (VBN called) (NP (JJ valence) (NNS electrons)))) (. .)))