list three differences between ions and isotopes?

Question

An ion is an atom that has at least one fewer electrons than it has protons. Thus, an ion always has positive charge. Hydrogen usually has one proton and one electron and has neutral charge. The hydrogen ion H+ has one proton and no electrons and has a positive charge. Isotopes are atoms that have more or less neutrons than protons. For instance, Carbon-12 has 6 protons and 6 neutrons, but Carbon-13 has 6 protons and 7 neutrons. Both Carbon-12 and Carbon-13 are isotopes of Carbon.

Although shish's answer is essentially correct, ions can also be negative. See:

http://web.jjay.cuny.edu/~acarpi/NSC/3-atoms.htm
http://www.visionlearning.com/library/module_viewer.php?c3=&mid=51&l

Essentially, an ion is an element with a varying number of electrons, while an isotope is an elements with a varying number of protons. Now, from the above sources, you need to determine what other differences these changes cause.

I hope this helps a little more. Thanks for asking.