Final answer:
a. 12. Magnesium has 12 protons, which corresponds to its atomic number. As a neutral magnesium atom, it also has 12 electrons and typically 12 neutrons. It has a somewhat reactive nature and tends to donate electrons due to its place as an alkaline earth metal.
Step-by-step explanation:
Magnesium (Mg) has an atomic number of 12, which means a neutral magnesium atom has 12 protons. The options listed a. 12, b. 2, c. 8, and d. 10 represent different numbers, but magnesium's atomic number directly tells us the number of protons in its nucleus, which corresponds to option a. 12. For a neutral atom, the number of electrons equals the number of protons, so a neutral magnesium atom will also have 12 electrons. As for neutrons, these can vary depending on the isotope; however, the most common isotope of magnesium has an atomic weight of about 24, and given that the atomic weight is roughly the sum of protons and neutrons, magnesium typically has 12 neutrons as well.
The complete electron configuration for a magnesium atom with 12 electrons is 1s² 2s² 2p¶ 3s². Magnesium plays a critical role in biological processes and is important for bone structure. While it is relatively stable, it is also fairly reactive; it tends to donate electrons when reacting with other atoms due to its two valence electrons, which makes it an alkaline earth metal.