This doesn't seem like it should be too hard, but i'm stuck... Am i making a stupid mistake somewhere? 1. The density of potassium metal is 0.89 g/cm3. Potassium's atomic radius is 231 pm. Assuming that r nuc = 10^-4 x r atom, estimate the density of an essentially spherical 39K nucleus. 2. Relevant equations Volume of a sphere 3. The attempt at a solution Convert pm to cm: 231 pm = 2.31E-8 cm Find number of grams in the whole atom by finding the volume of the atom and mulitplying it by the density: (4/3)(pi)(2.31E-8)^3 * .89 = 4.5953E-23 g Radius of nucleus = 1E-4 * 2.31E-8 cm = 2.31E-12 cm Volume of nucleus = (4/3)(pi)((2.31E-12)^3) = 5.1632666E-35 Find density by: 4.5953E-23/5.1632666E-35 = 8.899E11 g/cm^3 Unfortunately, that doesn't match with the answer given: The answer given is 1.26E12 g/cm^3 Thanks for any help.