Compounds are classified based on the nature of the chemical bond holding their constituent atoms together. This classification depends on how electrons are utilized between the atoms. Atoms interact to achieve stability by either sharing electrons or completely transferring them, leading to two distinct types of compounds. Understanding these bonding mechanisms is essential for determining the structural identity of any chemical substance.
What Makes a Compound Molecular
Molecular compounds, also called covalent compounds, are formed when atoms share electrons rather than transferring them. This sharing typically occurs between two or more nonmetal elements with a similar attraction for electrons. The shared electrons orbit the nuclei of both atoms, effectively binding them together into a stable unit.
This electron sharing results in the formation of distinct units called molecules. Because the forces between these individual molecules are relatively weak, molecular compounds generally exhibit low melting and boiling points. They do not conduct electricity because they lack free-moving charged particles.
What Makes a Compound Ionic
Ionic compounds are formed through the complete transfer of one or more electrons from one atom to another. This transfer creates charged particles known as ions: a positively charged cation and a negatively charged anion. The resulting strong electrostatic attraction between these oppositely charged ions forms the ionic bond.
Ionic bonds commonly form between a metal atom, which tends to lose electrons, and a nonmetal atom, which accepts electrons. Instead of forming discrete molecules, these compounds arrange themselves into a vast, ordered, three-dimensional structure called a crystal lattice. The strong forces within this lattice result in high melting and boiling points, and the solids are hard and brittle.
Analyzing Magnesium Chloride
To determine the identity of Magnesium Chloride (\(\text{MgCl}_2\)), we must first identify its constituent elements: Magnesium (\(\text{Mg}\)) and Chlorine (\(\text{Cl}\)). Magnesium is an alkaline earth metal found in Group 2, while Chlorine is a nonmetal found in Group 17. The interaction between a metal and a nonmetal is the primary indicator for the formation of an ionic bond.
The process begins with the Magnesium atom, which has two valence electrons it seeks to lose to achieve a stable electron configuration. It transfers these two electrons, becoming a positively charged magnesium ion, \(\text{Mg}^{2+}\).
Each Chlorine atom requires only one electron to complete its outer shell. Therefore, the two electrons lost by the single Magnesium atom are transferred to two separate Chlorine atoms. Each Chlorine atom accepts one electron and is converted into a negatively charged chloride ion, \(\text{Cl}^-\).
The resulting \(\text{Mg}^{2+}\) cation and the two \(\text{Cl}^-\) anions are held together by powerful electrostatic forces of attraction. Magnesium Chloride is classified as an ionic compound, and its structure is a crystal lattice of ions.