Carbon is allowed to diffuse through a steel plate 10-mm thick. The concentrations of carbon at the two faces are 0.815 and 0.277 kg C/m3 Fe, which are maintained constant. If the preexponential and activation energy are 6.5 × 10-7 m2/s and 82 kJ/mol, respectively, calculate the temperature (in K) at which the diffusion flux is 3.2 × 10-9 kg/(m2-s).

since electrons are negative the answer is neagtaive

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.