<h2>
Answer:</h2>
Average atomic mass of an element is the sum of the masses of its isotopes each multiplied by its natural abundance





Control rods are used<span> in </span>nuclear<span> reactors to </span>control<span> the fission rate of uranium and plutonium. They are composed of chemical elements such as boron, silver, indium and cadmium that are capable of absorbing many neutrons without themselves fissioning.</span>
From the conversion of units:
1 cm^3 is equivalent to 1 mL
1 L is equivalent to 1000 mL
therefore,
to convert from liter to cm^3, we simply multiply by 1000.
Note that the multiplication will be done in the denominator.
Based on this:
density = (0.625 g/l) x (1g/1000 cm^3) = <span> 0.000625 g/cm^3
= 6.25 x 10^-4 g/cm^3</span>