Atoms, the fundamental building blocks of matter, consist of a nucleus surrounded by electrons. While atoms possess an equal number of protons and electrons, giving them a neutral electrical charge, they can change to become electrically charged particles called ions. This article explains how a neutral magnesium atom transforms into a magnesium ion.
Understanding the Magnesium Atom
A neutral magnesium atom (Mg) has an atomic number of 12, meaning it contains 12 protons in its nucleus, which carry a positive electrical charge. In its neutral state, it also possesses 12 electrons, each carrying a negative electrical charge.
These 12 electrons are arranged in shells around the nucleus. The innermost shell holds two electrons, the second shell accommodates eight electrons, and the outermost valence shell contains the remaining two electrons.
The Transformation to an Ion
Atoms seek a more stable electron configuration by achieving a full outer electron shell. This principle, known as the octet rule, suggests atoms tend to gain, lose, or share electrons until they possess eight valence electrons. Magnesium, with its two valence electrons, achieves this stability differently.
Instead of gaining six electrons, which would be energetically unfavorable, magnesium finds it more efficient to lose its two outermost electrons. This removes these negatively charged particles and alters the atom’s electrical balance.
When the magnesium atom sheds these two valence electrons, its outermost shell becomes the previously full second shell, which already contains eight electrons. This new configuration provides the magnesium atom with a stable, full outer electron shell, mimicking the electron arrangement of a noble gas. This electron loss is a common chemical event, often occurring when magnesium reacts with other elements that readily accept electrons.
Characteristics of the Magnesium Ion
Once two valence electrons are lost, the magnesium atom transforms into a magnesium ion, denoted as Mg²⁺. The ion retains its 12 protons in the nucleus but now has only 10 electrons orbiting.
The imbalance between 12 positive charges and 10 negative charges results in a net electrical charge of +2. An atom or molecule that has lost electrons and carries a net positive charge is termed a cation.
The magnesium ion, Mg²⁺, exhibits properties significantly different from the neutral magnesium atom. Its ionic radius is smaller because the outermost electron shell is gone. The remaining electrons are pulled closer by the unchanged positive nuclear charge, creating a more compact structure.