( ( ( ( ( ( ( ( ( Ionic compounds ) ( are ( ( ( formed ( between ( ( metals and ) nonmetals ) ) ) , ) ( while ( ( covalent compounds ) ( are ( formed ( between ( two nonmetals ) ) ) ) ) ) ) ) ) , ) or ) , ) ( as ( is ( ( ( ( the case ) ( with ( tin tetraiodide ) ) ) , ) ( between ( ( an element ) ( that ( is ( ( a ( borderline metal ) ) ( -LRB- ( ( notice ( ( the position ) ( of ( tin ( on ( the ( periodic chart ) ) ) ) ) ) ) -RRB- ) ) ) ) ) ) ) ) ) ) ) and ) ( ( a nonmetal ) ( like iodine ) ) ) . )
(ROOT (S (S (NP (JJ Ionic) (NNS compounds)) (VP (VBP are) (VP (VBN formed) (PP (IN between) (NP (NNS metals) (CC and) (NNS nonmetals))) (, ,) (SBAR (IN while) (S (NP (NN covalent) (NNS compounds)) (VP (VBP are) (VP (VBN formed) (PP (IN between) (NP (CD two) (NNS nonmetals)))))))))) (, ,) (CC or) (, ,) (SBAR (IN as) (S (VP (VBZ is) (NP (NP (DT the) (NN case)) (PP (IN with) (NP (NN tin) (NN tetraiodide))) (, ,) (PP (IN between) (NP (NP (DT an) (NN element)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (NP (NP (DT a) (JJ borderline) (NN metal)) (PRN (-LRB- -LRB-) (S (VP (VB notice) (NP (NP (DT the) (NN position)) (PP (IN of) (NP (NP (NN tin)) (PP (IN on) (NP (DT the) (JJ periodic) (NN chart)))))))) (-RRB- -RRB-)))))))))))) (CC and) (S (NP (DT a) (NN nonmetal)) (PP (IN like) (NP (NN iodine)))) (. .)))
Ionic compounds are formed between metals and nonmetals, while covalent compounds are formed between two nonmetals, or, as is the case with tin tetraiodide, between an element that is a borderline metal (notice the position of tin on the periodic chart) and a nonmetal like iodine.
(ROOT (S (NP (NP (JJ Ionic) (NNS bonds)) (PP (IN between) (NP (CD two) (NNS atoms)))) (VP (VBP require) (NP (NP (CD one) (NN metal)) (CC and) (NP (CD one) (NN nonmetal)))) (. .)))