1. The problem statement, all variables and given/known data I am wondering about something: Calculate the Fermi energy for the neutrons confined to a nucleus with 40 protons and 50 neutrons which roughly forms a sphere of radius 4.6 10^(-15) m. 2. Relevant equations the formula of the fermi Energy is EF= ((h-bar)^2*(3*pi^2*n)^(2/3))/2m m:mass of electron, n = number density of electron 3. The attempt at a solution Then, in the problem we are given protons and neutrons. Where does influence the formula? and where do we use the radius there is one relation that is n = N/V ( N= protons+Neutrons) and V is the volume of the sphere. is it right? Also, do we use the mass of electron or the mass of proton = neutron this time?