Thermal decomposition of Mg(NO3)2 yields NO2 gas as one of the products. Let's break down the process and explain it in detail:

Thermal decomposition:
- Thermal decomposition is a chemical reaction in which a compound breaks down into simpler substances upon heating.
- In the case of Mg(NO3)2, when it is heated, it decomposes into its constituent elements or simpler compounds.

Decomposition of Mg(NO3)2:
- Mg(NO3)2 is composed of magnesium (Mg) and nitrate ions (NO3-).
- The chemical formula indicates that there are two nitrate ions present in the compound.
- Upon heating, the compound breaks down into its constituent elements and/or compounds.

Products of thermal decomposition:
- The decomposition of Mg(NO3)2 yields magnesium oxide (MgO) and nitrogen dioxide gas (NO2) as the products.
- The balanced equation for the reaction can be written as:
2Mg(NO3)2 → 2MgO + 4NO2 + O2

Explanation of the products:
1. Magnesium oxide (MgO):
- One of the products obtained is magnesium oxide (MgO).
- It is formed by the combination of magnesium (Mg) from Mg(NO3)2 and oxygen (O) from the nitrate ions.
- The balanced equation shows that two moles of Mg(NO3)2 yield two moles of MgO.

2. Nitrogen dioxide gas (NO2):
- The other product obtained is nitrogen dioxide gas (NO2).
- Nitrogen dioxide is formed by the decomposition of the nitrate ions (NO3-) present in Mg(NO3)2.
- The balanced equation shows that four moles of NO2 are produced for every two moles of Mg(NO3)2.

Other possibilities:
- The other options mentioned in the question, such as MgNO2, N2O, and NO, are not the correct products of the thermal decomposition of Mg(NO3)2.
- While magnesium nitrite (Mg(NO2)2) does exist, it is not formed as a product in this specific decomposition reaction.

In summary, when Mg(NO3)2 undergoes thermal decomposition, it yields magnesium oxide (MgO) and nitrogen dioxide gas (NO2) as the products.