Protons and neutrons have opposite, but equal magnitude, charges. An atom contains the same number of protons and electrons Neutrons and electrons are found in the nucleus of an atom. Protons have about the same mass as electrons. Electrons make up most of the mass of an atom. which one is true about subatomic particles

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.