Calculations:

Mass of Magnesium in the Magnesium Oxide Compound:

0.17 Mg x 1 mol Mg     = 7.0 x 10-3  mol Mg

    1         24.31 g Mg

Mass of Oxygen in the Magnesium Oxide:

0.276 g MgO - 0.17 g Mg = 0.106 g O

Mole of Oxygen in the Magnesium Oxide:

0.106 g O  x  1 mol O   = 0.001 mol O

     1            16.00 g O

Molar Ratio Between Oxygen and Magnesium:

O: 0.001 mol O  = 1

         0.001

Mg:  7.0 x 10-3  mol Mg = 7

               0.001

Molar Ratio: 1:7

Empirical Formula of the Magnesium Oxide Compound:

Mg7.00O1.00