Question

When molten sulfur reacts with chlorine gas, a vile-smelling orange liquid forms that has a formula of \(\mathrm{S}_{2} \mathrm{Cl}_{2}\). The Lewis structure of this compound has a formal charge of zero on all elements in the compound. Draw the Lewis structure for the vile-smelling orange liquid.

Short answer

The Lewis structure for the vile-smelling orange liquid S2Cl2 is drawn by following these steps: 1. Count the total number of valence electrons (26); 2. Determine the central atoms (2 sulfur atoms); 3. Place the remaining atoms around the central atom (2 chlorine atoms); 4. Distribute the electrons among the atoms to satisfy the octet rule: .. .. :Cl-S-S-Cl: .. .. 5. Check the formal charge: all atoms have a formal charge of zero, thus confirming that the Lewis structure is correct.

Step-by-step solution

Count the total number of valence electrons

Sulfur has 6 valence electrons (group 16) and chlorine has 7 (group 17). Since there are 2 sulfur atoms and 2 chlorine atoms in the compound, the total number of valence electrons is (6 x 2) + (7 x 2) = 12 + 14 = 26.

Determine the central atom

In this compound, sulfur is the central atom, as it can form more bonds than chlorine and is also less electronegative. We will be placing the 2 sulfur atoms in the center with the 2 chlorine atoms surrounding them.

Place the remaining atoms around the central atom

We place the chlorine atoms around the two central sulfur atoms. The two sulfur atoms will bond together as well. S - S | | Cl Cl

Distribute the electrons among the atoms to satisfy the octet rule

Distribute the remaining 22 electrons (26 provided minus 2 electrons in the S-S bond and 2 electrons in each S-Cl bond) to the chlorine atoms and the central sulfur atoms to satisfy the octet rule: .. .. :Cl-S-S-Cl: .. .. The octet rule is satisfied for each chlorine atom with a single bond to Sulfur of 2 shared electrons and 3 lone pairs (6 electrons). The octet rule is also satisfied for each sulfur atom with 2 shared electrons in the S-S bond, 2 electrons in each S-Cl bond, and 1 lone pair (2 electrons).

Check the formal charge

Now, let's verify that all the atoms in our drawn structure have a formal charge of zero. The formal charge is given by the formula: Formal charge = (number of valence electrons) - (number of non-bonding electrons) - 0.5 x (number of bonding electrons) For sulfur: Formal charge = (6) - (2) - 0.5 x (6) = 0 For chlorine: Formal charge = (7) - (6) - 0.5 x (2) = 0 All the atoms have a formal charge of zero, so our Lewis structure is correct.

Key concepts

Valence Electrons

Valence electrons are the outermost electrons in an atom and play a crucial role in bond formation. They are responsible for the chemical properties of an element.
Each element in the periodic table has a characteristic number of valence electrons based on its group number. For example:

• Sulfur (S) is in group 16, so it has 6 valence electrons.
• Chlorine (Cl) is in group 17, so it has 7 valence electrons.

When you are drawing a Lewis structure, it’s important to account for all the valence electrons in the molecule.
In the case of \( \text{S}_2 \text{Cl}_2 \), there are two atoms of sulfur and two atoms of chlorine. Therefore, the total number of valence electrons is calculated as follows:

• 2 sulfur atoms contribute \(2 \times 6 = 12\) electrons.
• 2 chlorine atoms contribute \(2 \times 7 = 14\) electrons.

This results in a total of 26 valence electrons to be used in the Lewis structure of \( \text{S}_2 \text{Cl}_2 \). Properly distributing these electrons is key to forming valid chemical bonds and ensuring the molecule's stability.

Octet Rule

The octet rule is a guiding principle in chemistry that helps explain how atoms bond. According to this rule, atoms are most stable when they have eight electrons in their valence shell, resembling the electron configuration of noble gases.
Let's explore how the octet rule applies:In \( \text{S}_2 \text{Cl}_2 \), chlorine atoms each need 8 electrons to satisfy the octet rule. They achieve this by forming single bonds with sulfur, sharing one pair of electrons:

• Each chlorine atom ends up with one bond (2 electrons) and three lone pairs (6 electrons), totaling 8 electrons.

Similarly, sulfur atoms also follow the octet rule but can expand beyond the octet due to the availability of d-orbitals.
For sulfur in \( \text{S}_2 \text{Cl}_2 \), each sulfur atom has one bond linking to another sulfur atom and two bonds to chlorine atoms. Each sulfur atom also retains a lone pair:

• Two pairs of shared electrons in bonds (S-S and S-Cl bonds) and one lone pair ensure that sulfur has access to an octet.

Understanding the octet rule is fundamental for predicting molecular structures and explaining the stability of molecules like \( \text{S}_2 \text{Cl}_2 \).

Formal Charge

Calculating the formal charge of an atom in a molecule helps to ensure that the Lewis structure is correct. A formal charge is an estimate of the electron charge distribution within a molecule. It can clarify which atoms hold more electron density.To calculate formal charge:

• Start with the number of valence electrons as per the periodic table.
• Subtract the number of electrons that are non-bonding (lone pairs).
• Subtract half of the bonded electrons (shared in bonds).

The formula used is: \[\text{Formal charge} = (\text{valence electrons}) - (\text{non-bonding electrons}) - 0.5 \times (\text{bonding electrons})\]In \( \text{S}_2 \text{Cl}_2 \), let's check:

• For sulfur: Suppose sulfur has 6 valence electrons, 2 are non-bonding, and 6 (from three bonds) are bonding.
  Formal charge: \(6 - 2 - 0.5 \times 6 = 0\).
• For chlorine: With 7 valence electrons, 6 non-bonding, and 2 bonding from its single bond.
  Formal charge: \(7 - 6 - 0.5 \times 2 = 0\).

A formal charge of zero ensures that the structure is both correct and stable. Comparing formal charges can further validate molecular configurations shown in Lewis structures.