Why is large-scale nuclear fission a rare phenomenon on Earth? A. There isn’t enough energy to start a chain reaction in nature. B. There are no naturally occurring atoms that can undergo fission left on Earth. C. Atoms that undergo fission aren’t concentrated enough to sustain a chain reaction. D. Atoms that undergo fission tend to decay more slowly on Earth than in stars.

The content of manganese (mn) in steel was determined spectrophotometrically and with the use of the standard addition method. an unknown sample of mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. when 5.00 ml of solution containing 95.5 ppm mn was added to 50.0 ml of the unknown steel solution (digested sample), the absorbance was 0.248. calculate the concentration, in parts-per-million (ppm), of mn in the digested steel sample solution.