How many valence electrons are in an atom of magnesium (atomic number 12)
The correct answer and explanation is:
Correct Answer: 2 valence electrons
Magnesium is a chemical element with the atomic number 12. This means that a neutral atom of magnesium contains 12 protons in its nucleus and 12 electrons surrounding the nucleus. These electrons are arranged in energy levels, also known as electron shells.
The first energy level, closest to the nucleus, can hold a maximum of 2 electrons. The second level can hold up to 8 electrons. The remaining 2 electrons go into the third energy level. This gives magnesium the electron configuration of 2 in the first shell, 8 in the second shell, and 2 in the third shell. Therefore, magnesium has 2 electrons in its outermost shell, which are called valence electrons.
Valence electrons are important because they are the electrons involved in chemical bonding. Elements tend to form bonds in such a way that they achieve a full outer shell of electrons, which gives them a more stable configuration. Magnesium, with its 2 valence electrons, often reacts by losing those two electrons. When it loses these electrons, it achieves the stable electron configuration of neon, a noble gas with a full outer shell.
By losing 2 electrons, magnesium forms a +2 ion, known as Mg²⁺. This ion is stable and often found in ionic compounds like magnesium chloride (MgCl₂). The ability of magnesium to lose its valence electrons easily is one reason it is classified as an alkaline earth metal and is highly reactive, especially with nonmetals like oxygen and chlorine.
In summary, a neutral atom of magnesium has 2 valence electrons, located in the third energy level. These electrons determine magnesium’s chemical behavior and allow it to form stable compounds by participating in reactions that involve the transfer of electrons.