1. The problem statement, all variables and given/known data The resistivities and Fermi speeds of Na, Au, and Sn at T = 273 K are 4.2 µ[tex]\Omega[/tex]·cm, 2.04 µ[tex]\Omega[/tex]·cm, and 10.6 µ[tex]\Omega[/tex]·cm, and 1.07e6 m/s, 1.39e6 m/s, and 1.89e6 m/s respectively. Use these values to find the mean free paths λ for the conduction electrons in these elements. 2. Relevant equations 3. The attempt at a solution I think the equation I should be using is [tex]\rho[/tex]=(Me)(Vav)/(Ne)(e)^2[tex]\lambda[/tex]. The main issue with this problem is that the units are all over the place. Using this equation, I get [tex]\lambda[/tex]= 3.56nm for Na. All I'm concerned with right now is Na. I have a feeling though that since I am given the Fermi speed, I need to use a formula that incorporates the Fermi speed, but I cannot find any that seem relevant.