( So ( scientists ( ( ( describe ( their positions ) ) ( in ( terms ( of ( ( ( orbitals -- ) essentially ) ( regions ( ( in which ) ( electrons ( are ( most ( likely ( to ( be ( found ( as ( they ( whiz ( around ( atomic nuclei ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) ) )
(ROOT (S (IN So) (NP (NNS scientists)) (VP (VBP describe) (NP (PRP$ their) (NNS positions)) (PP (IN in) (NP (NP (NNS terms)) (PP (IN of) (NP (NP (NNS orbitals)) (: --) (RB essentially) (NP (NP (NNS regions)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (NNS electrons)) (VP (VBP are) (ADJP (RBS most) (JJ likely) (S (VP (TO to) (VP (VB be) (VP (VBN found) (SBAR (IN as) (S (NP (PRP they)) (VP (VBZ whiz) (PP (IN around) (NP (JJ atomic) (NNS nuclei)))))))))))))))))))) (. .)))
So scientists describe their positions in terms of orbitals--essentially regions in which electrons are most likely to be found as they whiz around atomic nuclei.
(ROOT (S (NP (DT The) (NN orbital)) (VP (VBZ is) (NP (NP (DT the) (NN area)) (SBAR (WHADVP (WRB where)) (S (NP (DT an) (NN electron)) (VP (VBZ is) (ADJP (RBS most) (JJ likely) (S (VP (TO to) (VP (VB be) (VP (VBN found))))))))))) (. .)))