So now we'll talk about problems. 58 from chapter four. This problem, whereas how do isotopes differ? And how are they similar isotopes for the same element. So isotopes differ in the number of neutrons. So of course, the number of neutrons being different also means that the mess number will be different. However, they are the same for the same element. Different isotopes Ah, and the number of protons and electrons and also atomic number, which is the same thing as the number of protons.