The answer is
. A magnesium atom has 12 protons and an arrangement of [2, 8, 2]. When you lose two electrons, arrangement becomes [2,8] and the atom becomes a positively charged ion
In order of increasing percent water content:CoCl₂.6H₂O, Ba(OH)₂.8H₂O, MgSO₄.7H₂O
<h3>Further explanation</h3>

CoCl₂.6H₂O.MW=237.90 g/mol
6H₂O MW = 6.18=108 g/mol

MgSO₄.7H₂O.MW=246.48 g/mol
MW 7H₂O = 7.18=126 g/mol

Ba(OH)₂.8H₂O MW=315.48 g/mol
MW 8H₂O = 8.18=144 g/mol

After careful consideration your answer is...
Leucippus and Democritus
*Hope I helped*
~Alanna~