I understand that this deviation from the general trend of increasing atomic number and atomic mass is because cobalt's isotopes tend to have more neutrons than nickel's. Why is that the case? How would one go about predicting similar cases like this?

I understand that this deviation from the general trend of increasing atomic number and atomic mass is because cobalt's isotopes tend to have more neutrons than nickel's. Why is that the case? How would one go about predicting similar cases like this?

I've read a bit about the shell model. I understand that 28 is a "magic number" of nucleons, i.e. a filled shell. In that case, wouldn't it be the most stable for both atoms to mainly be found with 28 neutrons; and so, cobalt-55 and nickel-56 would be the most stable isotopes of each element. Why is that not the case? Am I missing or misunderstanding something?

I understand that this deviation from the general trend of increasing atomic number and atomic mass is because Cobalt's isotopes tend to have more neutrons than Nickel's. Why is that the case? How would one go about predicting similar cases like this?

I understand that this deviation from the general trend of increasing atomic number and atomic mass is because cobalt's isotopes tend to have more neutrons than nickel's. Why is that the case? How would one go about predicting similar cases like this?