, ▁but ▁not ▁yet ▁detected ▁ne on ium , ▁Ne H + ▁( pro ton ated ▁ne on ) ▁arg on ium , ▁Ar H + ▁( pro ton ated ▁arg on ) ▁k rypt on ium , ▁Kr H + ▁( pro ton ated ▁k rypt on ) ▁x en on ium , ▁X e H + ▁( pro ton ated ▁x en on ) ▁ ▁H ydro gen ▁on ium ▁c ation ▁hydro gen on ium , ▁better ▁known ▁as ▁tri h ydro gen ▁c ation , ▁H ▁( pro ton ated ▁[ m ole cular ] ▁or ▁[ di atomic ] ▁hydro gen ), ▁found ▁in ▁ion ized ▁hydro gen ▁and ▁inter stell ar ▁space ▁ ▁O ni um ▁c ations ▁with ▁mon oval ent ▁substitution s ▁primary ▁am mon ium ▁c ations , ▁R H 3 N + ▁or ▁R N H ▁( pro ton ated ▁primary ▁am ines ) ▁hydro x yl am mon ium , ▁N H 3 OH + ▁( pro ton ated ▁hydro x yl am ine ) ▁m eth yl am mon ium , ▁CH 3 N H ▁( pro ton ated ▁m eth yl am ine ) ▁eth yl am mon ium , ▁C 2 H 5 N H ▁( pro ton ated ▁eth yl am ine ) ▁hyd raz in ium , ▁or ▁dia zan ium , ▁N H 2 N H ▁( pro ton ated ▁hyd raz ine , ▁a . k . a . ▁dia z ane ) ▁secondary ▁am