( Atoms ( ( ( ( are electrically ) ( neutral ( when ( ( ( the number ) ( of ( ( ( negatively charged ) electrons ) ( orbiting ( the nucleus ) ) ) ) ) ( equals ( ( the number ) ( of ( ( positively charged ) protons ) ) ) ) ) ) ) ) ( within ( the nucleus ) ) ) . ) )
(ROOT (S (NP (NNS Atoms)) (VP (VBP are) (ADVP (RB electrically)) (ADJP (JJ neutral) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NP (ADJP (ADVP (RB negatively)) (VBN charged)) (NNS electrons)) (VP (VBG orbiting) (NP (DT the) (NN nucleus)))))) (VP (VBZ equals) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (ADJP (ADVP (RB positively)) (VBN charged)) (NNS protons)))))))) (PP (IN within) (NP (DT the) (NN nucleus)))) (. .)))
Atoms are electrically neutral when the number of negatively charged electrons  orbiting the nucleus equals the number of positively charged protons within the nucleus.
(ROOT (S (SBAR (IN Because) (S (NP (NNS atoms)) (VP (VBP have) (NP (NP (JJ equal) (NNS numbers)) (PP (IN of) (NP (NP (JJ positive) (NNS protons)) (CC and) (NP (JJ negative) (NNS electrons)))))))) (, ,) (NP (PRP they)) (VP (VBP possess) (NP (DT a) (JJ neutral) (NN charge))) (. .)))