Calculating the mass of magnesium in the magnesium oxide compound, and the number of moles of magnesium in the compound:

Calculating the mass and number of moles of oxygen in the magnesium oxide:

The molar ratio between magnesium and oxygen is 0.0086/0.0078 = 1.10, or a ratio of 1:1.  The empirical formula of the magnesium oxide compound using whole numbers is also 1:1.