Problem 10 - Chemistry A Guided Inquiry

Question

For \(\mathrm{Cl}_{2}\), is the sum of the bonding electrons and the lone pair electrons (also known as nonbonding electrons) around each Cl atom consistent with the Lewis model?

Step-by-Step Solution

Answer

Yes, the sum of the bonding and nonbonding electrons around each Cl atom in the \(\mathrm{Cl}_{2}\) molecule is consistent with the Lewis model since each Cl atom achieves a full octet by sharing an electron.

Step 1: Know what the Lewis model expects

According to the Lewis model, atoms will form bonds until they reach a stable electron configuration, most commonly a full octet (eight). Thus, the sum of the bonding and nonbonding electrons should be consistently around 8 for each atom in relation to this exercise.

Step 2: Determine the electron configuration of Cl

Chlorine has 7 valence electrons. In the Cl2 molecule, each chlorine atom shares one electron with the other, creating a single bond. So each Cl atom in the molecule has 1 bonding electron and 6 nonbonding electrons.

Step 3: Verify if it is consistent with the Lewis model

The sum of the bonding and nonbonding electrons for each Cl atom is 1 + 6 = 7 which is less than an octet (8). However, as the shared electron is counted for each Cl atom separately, essentially, each Cl atom has a full octet. So our observation is consistent with the Lewis model.

Key Concepts

Bonding Electrons

Bonding electrons play a pivotal role in the formation and stability of molecules. When we refer to bonding electrons, we're talking about those electrons that are shared between atoms, creating a bond. These bonds are what hold atoms together in a molecule. In the case of diatomic chlorine (\(\mathrm{Cl}_2\)), each chlorine atom contributes one electron to form a single covalent bond, which is represented by a line connecting the two chlorine atoms in the Lewis structure. This pairing of electrons gives each atom access to more electrons than it has individually, helping it to reach a stable state, often referred to as the 'octet rule'. This rule reflects the observation that atoms tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas.

In evaluating \(\mathrm{Cl}_2\), by considering each bonding electron pair as a shared resource, we see that each Cl atom indeed reaches an octet, thus adhering to the Lewis model. Understanding the concept of bonding electrons can be crucial when predicting the geometrical structure of molecules and their reactivity patterns.

Lone Pair Electrons

Lone pair electrons, also known as nonbonding electrons, are valence electrons that are not shared between atoms and instead remain localized on a single atom. These electrons still play an important role by affecting the shape and reactivity of the molecule. In a \(\mathrm{Cl}_2\) molecule, each chlorine atom has three lone pairs, amounting to six nonbonding electrons. These electrons occupy more space around the chlorine nucleus because they are not shared with another atom, which can push against bonding pairs and influence molecular geometry through repulsion forces. It's important to remember that even though these electrons don't contribute to bonding, they do contribute to the atom's stability by fulfilling the requirement for a complete octet in the valence shell. When examining a Lewis structure, lone pairs are typically represented as dots around the atom to distinguish them from bonding pairs.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial to determining an atom's chemical properties and reactivity. These electrons can participate in the formation of chemical bonds, whether by sharing electrons with other atoms to form covalent bonds, or by transferring electrons in ionic bonds. The number of valence electrons that an atom possesses defines how it interacts with other atoms and forms compounds. In the case of chlorine in \(\mathrm{Cl}_2\), each atom has seven valence electrons. During the process of bond formation, each chlorine atom's one valence electron is used for bonding, and the remaining six constitute the lone pairs. This distribution of electrons is reflected in the Lewis model, which is a visual representation of the possible distribution of these valence electrons around an atom.

Electron Configuration

The electron configuration of an atom describes the distribution of electrons in the atom's orbitals. It determines how these electrons are arranged around the nucleus and is key to understanding an atom's reactivity and the types of bonds it can form. For example, chlorine has the electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^5\), showing that it has seven electrons in its outermost shell, which are its valence electrons. When chlorine atoms approach each other to form a \(\mathrm{Cl}_2\) molecule, each uses one of its valence electrons to form the single covalent bond. The concept of electron configuration extends beyond just knowing the number of electrons, as the configuration affects the atom's overall stability and its potential to form different chemical bonds.