Hydrogen has one proton in it's nucleus but exists as three isotopes. one isotope has no neutrons. one has one neutron, and one has two neutrons. how would they be identified using isotope notation? !

The Isotope Notation occur by adding the Superscript showing Mass Number and Subscript showing Atomic Number to the Left of the Element Symbol.

Example,

                                                 ᵇₐX
                        
                                   Where;
                                                b = Mass Number
                                                a = Atomic Number
                                               X  = Symbol
For Hydrogen Isotopes:

1) Protium: 1 Proton , 0 Neutron

                                                ¹₁H

2) Deuterium: 1 Proton , 1 Neutron

                                                ²₁H

3) Tritium: 1 Proton , 2 Neutron

                                                ³₁H

The mass has escaped into a gas which you can not see so the law stays true.

500bc indiais the answer.