Issued as a cumulative or non-cumulative L/C, the former allows for unused credit amounts to rollover into subsequent periods while the latter maintains a fixed amount of credit available each period.
average atomic mass of magnesium is 24.3 g/mole so 24.3 X 1.56 X1021 / 6.02 X1023 = .063 grams.
Magnesium Isotopes Mg-25 and Mg-26 are used to study the absorption and metabolism of Mg in the human body and they are also used for heart disease studies. Mg-25 is also used for the production of the radioisotope Na-22.