An ion is an atom or group of atoms in which the number of electrons is not equal to the number of protons, giving it a net positive or negative electrical charge.
Due to this, anoin which is a negatively charged and is attracted to the anode (positive electrode) in electrolysis. and is considered as a proton. however Cations are positively charged and are attracted to cation ( negative electrode). its know as a electron .
So, the net positive or negative electrical charge explains the difference in the amounts of phosphate and strontium.
An ion can never have the same amount of anions and cations.