* Magnesium (Mg) and Sodium (Na) are different elements. They have different numbers of protons in their nuclei. Magnesium has 12 protons, while sodium has 11 protons.

* Elements cannot transform into other elements through simple chemical reactions. The number of protons in an atom's nucleus defines what element it is. Changing the number of protons requires nuclear reactions, which are much more energetic than ordinary chemical reactions.

What might be happening?

The question likely describes a scenario involving a chemical reaction, but it's worded incorrectly. It's possible that:

* Magnesium is reacting with another element. Magnesium is a reactive metal and can react with various substances to form compounds. For example, it can react with oxygen to form magnesium oxide (MgO), releasing heat and light.

* The "second" being produced is a product of the reaction. This product could be a gas, a solid, or a liquid depending on the other reactant.

To understand the specific reaction, you need more information about the conditions and the other reactant involved.