Final answer:
The hyphen notation of an isotope after the removal of one proton involves lowering the atomic number by one to identify the new element and reducing the mass number by one, resulting in the new isotope notation.
Step-by-step explanation:
The student is asking about the change in an isotope's hyphen notation after the removal of one proton. To correctly write the new hyphen notation, you must determine the new element and its mass number after the loss of a proton (which also means the loss of one unit of mass). For example, if we remove one proton from the isotope nickel-59 (Ni-59), the atomic number decreases by one, thus changing the element to cobalt. The new isotope would then be cobalt-58 or Co-58, as the atomic mass decreases by one due to the loss of the proton.