can someone please explain to me how can Phosphorus and other elements have different number of bonding regions if the elements is still the same and no ionic charged is included this might be the only thing in chemistry I don't seem to understand like mathematically speaking its impossible I understand that in the third shell the maximum number of electrons is 18 but how can phosphorus for example form PCL3 AND PCL5 like how am I supposed to know how many bonding regions will there be if we are told that we should have 8 electrons max in an atom is my hypothesis of it being about the electron shell rule as in the third shell can have 18 so it can have as many bonding regions as it wants