Question

Consider the \(\mathrm{SCl}_{2}\) molecule. (a) What is the electron configuration of an isolated \(\mathrm{S}\) atom? (b) What is the electron configuration of an isolated \(\mathrm{Cl}\) atom? (c) What hybrid orbitals should be constructed on the \(S\) atom to make the \(\mathrm{S}-\mathrm{Cl}\) bonds in \(\mathrm{SCl}_{2}\) ? (d) What valence orbitals, if any, remain unhybridized on the \(\mathrm{S}\) atom in \(\mathrm{SCl}_{2}\) ?

Short answer

(a) The electron configuration of an isolated Sulfur (S) atom is: \(1s^2 2s^2 2p^6 3s^2 3p^4\). (b) The electron configuration of an isolated Chlorine (Cl) atom is: \(1s^2 2s^2 2p^6 3s^2 3p^5\). (c) In SCl₂, the Sulfur atom undergoes hybridization to form two \(sp^2\) hybrid orbitals that participate in bond formation with two Cl atoms. (d) After the \(sp^2\) hybridization, the remaining unhybridized valence orbitals on the Sulfur atom are one 3p orbital and one 3d orbital.

Step-by-step solution

(a) Electron configuration of an isolated Sulfur (S) atom

To determine the electron configuration of an isolated Sulfur atom, we need to know its atomic number, which is 16. The electron configuration can be represented as: \[1s^2 2s^2 2p^6 3s^2 3p^4\]

(b) Electron configuration of an isolated Chlorine (Cl) atom

For a Chlorine atom, the atomic number is 17. Its electron configuration is: \[1s^2 2s^2 2p^6 3s^2 3p^5\]

(c) Hybrid orbitals for S-Cl bonds in SCl₂

In SCl₂, Sulfur is the central atom which bonds with two Chlorine atoms. Sulfur has 6 valence electrons (3s², 3p⁴), and Chlorine has 7 valence electrons (3s², 3p⁵). To form two S-Cl bonds, the Sulfur atom needs two unpaired electrons that can participate in bonding. This can be achieved through hybridization. The Sulfur atom undergoes hybridization to form two \(sp^2\) hybrid orbitals in SCl₂. The 3s and two of the 3p orbitals on the S atom combine to form the \(sp^2\) hybrid orbitals that participate in bond formation with two Cl atoms.

(d) Unhybridized valence orbitals on the Sulfur atom in SCl₂

After the \(sp^2\) hybridization, the remaining valence orbitals on the Sulfur atom are one 3p orbital and one 3d orbital. The 3p orbital remains unhybridized as it does not participate in the bond formation. The 3d orbital is also unhybridized, as there are no d-electrons in the valence shell of Sulfur.

Key concepts

Hybridization

Hybridization is a concept that explains the mixing of atomic orbitals in an atom to form new hybrid orbitals. These hybrid orbitals have different shapes and energies compared to the original atomic orbitals. For example, in the case of sulfur in the \(\text{SCl}_2\) molecule, sulfur undergoes hybridization to facilitate bonding with chlorine.
To form the two \(\text{S-Cl}\) bonds, sulfur utilizes its valence orbitals. Hybrids like \(sp, sp^2,\) or \(sp^3\) are examples of how orbitals combine.
In \(\text{SCl}_2\), sulfur's \(3s\) and two \(3p\) orbitals mix to form \(sp^2\) hybrid orbitals. These \(sp^2\) hybrid orbitals have one part \(s\) character and two parts \(p\) character, providing an effective way to participate in covalent bonding.
The concept of hybridization simplifies understanding of molecular geometries and bond angles, allowing clearer predictions of molecular structure.

Valence Electrons

Valence electrons are the outermost electrons of an atom and play a major role in chemical bonding. They are crucial because they are most involved in interactions with other atoms.
For sulfur, which has an atomic number of 16, this means it has 6 valence electrons. The electronic configuration is \[1s^2 2s^2 2p^6 3s^2 3p^4\]. The \(3s^2 3p^4\) electrons are the valence electrons, which sulfur uses to form bonds.
Chlorine, having an atomic number of 17, has 7 valence electrons with the configuration: \[1s^2 2s^2 2p^6 3s^2 3p^5\]. In \(\text{SCl}_2\), chlorine uses its valence electrons to bond with sulfur. The number of these electrons determines how atoms can bond and with how many other atoms.
Understanding the count and arrangement of valence electrons is key to explaining the chemical properties and reactivity of elements.

Sulfur and Chlorine Atoms

Sulfur and chlorine are both non-metal elements. They each belong to periods and groups in the periodic table that define their properties. Sulfur is located in the third period and group 16 of the periodic table. It belongs to the chalcogens, a group known for forming compounds like sulfides and oxides.
Chlorine, on the other hand, is in the same period but group 17, known as the halogens. Halogens are very reactive and often form salts with metals.
The properties of these elements are pivotal in determining their interactions and the kinds of compounds they form, such as \(\text{SCl}_2\).
In molecules like \(\text{SCl}_2\), sulfur acts as a central atom allowing the formation of two covalent bonds with two chlorine atoms. These atoms arrange themselves in a way that optimizes the molecule's shape, leading to specific angles and spatial configurations, influenced by hybridization processes. Understanding these concepts allows for predicting molecular behavior in chemical reactions.