Chemistry Regents Review Question!?

Isotopes have the same proton/atomic number (the smaller number and on bottom) but different mass numbers (the larger number and on top). Basically chromium has a normal mass number of 52 and atomic number 24, so an isotope of it would be atomic number 24 (on bottom) and any number other than 52 on top (+or -), for example, 53, 51,etc. Hope that helped!