1. The problem statement, all variables and given/known data We must calculate the Fermi energy of metallic potassium at 0K. We have aleady found the number of atoms per m cubed, we are told that each atom contributes one electron to the free electron gas. 2. Relevant equations Fermi energy = ((hbar^2)/2m)(((3Pi^2)N)/V)^3/2 3. The attempt at a solution My problem is that i dont know what V is supposed to be. I thought that since each K gives one electron to become K+, V might be +e, but that gave a nonsensical answer.