( ( The cation ) ( ( ( ( comes first ) , ) ( both ( ( ( in ( the name ) ) and ) ( in ( ( the formula ) ( for ( an ( ionic compound ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN cation)) (VP (VBZ comes) (ADVP (RB first)) (, ,) (PP (DT both) (PP (IN in) (NP (DT the) (NN name))) (CC and) (PP (IN in) (NP (NP (DT the) (NN formula)) (PP (IN for) (NP (DT an) (JJ ionic) (NN compound))))))) (. .)))
The cation comes first, both in the name and in the formula for an ionic compound.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (VP (VBG naming) (NP (DT an) (JJ ionic) (NN compound))))) (, ,) (NP (DT the) (NN cation)) (VP (VBZ is) (VP (VBN written) (ADVP (RB first)))) (. .)))
When naming an ionic compound, the cation is written first.