Question

Write Lewis structures for the reaction $$ \mathrm{AlCl}_{3}+\mathrm{Cl}^{-} \longrightarrow \mathrm{AlCl}_{4}^{-} $$ What kind of bond is between \(\mathrm{Al}\) and \(\mathrm{Cl}\) in the product?

Short answer

In the product, \(AlCl_4^{-}\), the bond between Al and Cl is an ionic bond.

Step-by-step solution

Interpret the chemical equation

Looking at the equation \(AlCl_3 + Cl^- \rightarrow AlCl_4^-\), it shows that an aluminum chloride molecule is interacting with a chloride ion to form a tetrahedral aluminum chloride ion.

Drawing the Lewis structure of Initial Reactants

Al (Aluminum) has 3 valence electrons and Cl (Chloride) has 7 valence electrons. In \(AlCl_3\), Al utilizes its 3 valence electrons to form 3 bonds with three separate Cl atoms, each providing an electron, making it a neutral species. For \(Cl^{-}\), adding an extra electron to the 7 valence electrons of Cl makes it 8, which completes its octet, making it a negatively charged ion.

Drawing the Lewis Structure for the Final Product

The product of the reaction is \(AlCl_4^{-}\). The incoming Cl^- forms a bond with the existing aluminum ion by providing one additional electron. Now, the aluminum atom has an electron octet but carries a negative charge because it takes one electron more than it has in its valence shell.

Identifying the type of bond

The bond between Al and Cl in the product \(AlCl_4^{-}\) are ionic in nature because of the transfer of electrons from chloride ions to the aluminum ion.

Key concepts

Chemical Bonding

Chemical bonding is the fascinating interaction that holds atoms together in compounds. Atoms join together to become more stable, and there are different types of bonding based on how they share or transfer their valence electrons. One major category of chemical bonding is ionic bonding, which involves the transfer of electrons from one atom to another. This often occurs between metals and nonmetals, leading to the formation of a compound with unique properties compared to its individual atoms. Understanding chemical bonds helps us predict the structure and reactivity of different substances, making it a fundamental concept in chemistry.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial in the chemical bonding process. These electrons determine how an atom will bond because they are less tightly held by the nucleus and are more easily shared or transferred during chemical reactions. The number of valence electrons can influence the number of bonds an atom can form, and whether those bonds will be covalent, ionic, or even metallic in nature.

Here's a quick breakdown:

• Atoms with fewer than eight valence electrons tend to form bonds to attain a complete octet, like in noble gases.
• Metals tend to lose their valence electrons, while non-metals often seek to gain additional electrons through bonding.
• Understanding how many valence electrons an element has can predict its behavior during bonding, such as in the formation of ionic compounds like \( \text{AlCl}_4^- \).

Ionic Bonds

Ionic bonds are formed when one atom gives up one or more electrons to another atom. This type of bond is typical in the interaction between metals and nonmetals, such as aluminum and chlorine in the \( \text{AlCl}_4^- \) ion. Aluminum (Al), acting as a metal, typically loses electrons, while chlorine (Cl), a nonmetal, gains electrons. The electron transfer results in the formation of ions: positivé for Al due to electron loss and negativé for Cl due to electron gain.

This electron movement creates charged ions that attract each other, leading to a stable ionic compound. Ionic bonds are characterized by their strength and high melting points, as electrostatic forces hold the ions firmly in place. Importantly, in chemical reactions that form ionic bonds, individual ion charges balance to create a neutral overall charge, even when, as in \( \text{AlCl}_4^- \), an ion remains negatively charged on a molecular scale.