Which of the following represents magnesium nitrate?

Magnesium nitrate is represented by the formula Mg(NO3)2. This compound is made up of magnesium ions (Mg^2+) and nitrate ions (NO3^-). The nitrate ion carries a -1 charge, so to balance the +2 charge of the magnesium ion, two nitrate ions are required. This results in the formula Mg(NO3)2, indicating that for every magnesium ion, there are two nitrate ions attached to it.

The other formulas listed do not accurately represent magnesium nitrate. For instance, Mg(NO2)2 refers to magnesium nitrite, which is a different compound entirely. Similarly, MgN2O6 doesn't conform to the typical nomenclature used for magnesium salts, and Mg(NO3)3 suggests that there would be three nitrate ions which does not balance with the +2 charge of magnesium since it would imply a +3 cation. Thus, Mg(NO3)2 is the only correct representation of magnesium nitrate among the options.