2 – O – ), ▁with ▁six ▁acid ic ▁hyd rog ens . ▁ ▁Form s ▁t et raph osph ates . ▁ ▁The back bone ▁may ▁be ▁branch ed , ▁as ▁in ▁▁▁ ▁tri ph osph ono ▁ph osph or ic ▁acid , ▁ ▁or ▁P ( O )( – ) 3 , ▁a ▁branch ed ▁is omer ▁of ▁t et rap oly ph osph or ic ▁acid . ▁ ▁The ▁ ▁t etra hed ra ▁may ▁be ▁connected ▁to ▁form ▁closed ▁– P – O – ▁ch ains , ▁as ▁in ▁▁ ▁Tr imet aph osph or ic , ▁or ▁cy clo - tri ph osph or ic ▁acid , ▁ ▁( or ▁, ▁( – P ( O )( OH ) – O – ) 3 ), ▁a ▁cy clic ▁mole c ule ▁with ▁three ▁acid ic ▁hyd rog ens . ▁Form s ▁the ▁trim et aph osph ate ▁sal ts ▁and ▁est ers . ▁ ▁Met aph osph or ic ▁acid ▁is ▁general ▁term ▁for ▁ph osph or ic ▁ac ids ▁with ▁a ▁single ▁cycle , ▁( – P ( O )( OH ) – O – ) n , ▁whose ▁element al ▁formula ▁is ▁ ▁. ▁ ▁Another ▁comp ound ▁that ▁may ▁be ▁included ▁in ▁this ▁class ▁is ▁▁ ▁Pero x omon oph osph or ic ▁acid , ▁H 3 PO 5 ▁( or ▁OP ( OH ) 2 ( O OH )), ▁which ▁can ▁be ▁seen ▁as ▁mon oph osph or ic ▁acid ▁with ▁a ▁per ox