The solubility product of Mg(OH)2 is 1.2 × 10-11. What minimum OH^- concentration must be attained (for example, by adding NaOH) to decrease the Mg^2+ concentration in a solution of Mg(NO3)2 to less than 1.0 × 10-3 M FeSO4.

your answer would be a. 12.5 kg

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8