Group 2 metal atoms (Mg, Ca, Sr, and Ba) react on ultraviolet photoexcitation with O-2, H-2 mixtures in solid argon at 10 K to produce new absorptions in the O-H and O-M-O stretching regions. The effect of detailed isotopic substitution on these two absorptions identifies the M(OH)(2) molecules. The stepwise decrease in the O-H stretching modes in this chemical family demonstrates an increase in ionic character, which parallels the increase in base strength for the analogous solid compounds.