Question

(a) Does \(\mathrm{SCl}_{2}\) have a dipole moment? If so, in which direction does the net dipole point? (b) Does \(\mathrm{BeCl}_{2}\) have a dipole moment? If so, in which direction does the net dipole point?

Short answer

(a) Yes, SCl\(_2\) has a dipole moment. The net dipole points towards the chlorine atoms. (b) No, BeCl\(_2\) does not have a dipole moment due to its linear geometry.

Step-by-step solution

SCl2:

Sulfur has 6 valence electrons, and chlorine has 7. SCl2 has 20 electrons in total (6 from sulfur, 2*7 from chlorine). To find the molecular geometry, place sulfur in the center and attach the two chlorine atoms. Since there are two lone pairs on sulfur and two bonding pairs, the molecular geometry of SCl2 is bent (V-shaped). Now we need to find if there is a net difference in electronegativity between sulfur and chlorine.

Electronegativity:

Looking at the periodic table, we can find the electronegativity for sulfur and chlorine. Sulfur: 2.58 and Chlorine: 3.16. So there's a net difference in electronegativity between sulfur and chlorine (3.16 - 2.58 = 0.58).

Dipole moment of SCl2:

Since there is a net difference in electronegativity between sulfur and chlorine and the molecular geometry is bent, SCl2 will have a dipole moment. The direction of the net dipole will point toward the chlorine atoms, as chlorine is more electronegative than sulfur.

BeCl2:

Beryllium has 2 valence electrons and chlorine has 7. BeCl2 has 16 electrons in total (2 from beryllium, 2*7 from chlorine). To find the molecular geometry, place beryllium in the center and attach the two chlorine atoms. Since there are no lone pairs on beryllium and two bonding pairs, the molecular geometry of BeCl2 is linear.

Electronegativity:

Looking at the periodic table, we can find the electronegativity for beryllium and chlorine. Beryllium: 1.57 and Chlorine: 3.16. So there's a net difference in electronegativity between beryllium and chlorine (3.16 - 1.57 = 1.59).

Dipole moment of BeCl2:

Although there is a net difference in electronegativity between Be and Cl, BeCl2 molecule has a linear molecular geometry, which results in the cancellation of individual dipole moments. Due to this cancellation, BeCl2 does not have a net dipole moment. In conclusion, SCl2 has a dipole moment and the net dipole points towards the chlorine atoms. BeCl2 does not have a dipole moment due to its linear geometry.

Key concepts

Molecular Geometry

Molecular geometry essentially refers to the 3D arrangement of atoms within a molecule. This arrangement is pivotal in determining the molecule's shape as well as its physical and chemical properties.

The specific geometry a molecule adopts can be influenced by various factors, including the number of atoms, lone electron pairs, and the type of bonds.

• SCl2: In sulfur dichloride (SCl2), we see a bent or V-shaped geometry. This is due to the presence of two lone pairs on the sulfur atom, which push the chlorine atoms down, resulting in this shape.
• BeCl2: For beryllium dichloride (BeCl2), the molecular geometry is linear. Beryllium forms covalent bonds with two chlorine atoms, and having no lone pairs allows these bonds to align in a straight line, forming a linear shape.

Different geometries heavily influence whether or not a molecule will have a dipole moment.

Electronegativity

Electronegativity is a measure of how strongly an atom can attract and hold onto electrons within a bond. The higher the electronegativity, the stronger the atom attracts electrons.

This concept is crucial for understanding bond polarity, which is a fundamental part of determining whether a molecule has a dipole moment.

• SCl2: In SCl2, sulfur has an electronegativity of 2.58, whereas chlorine's is 3.16. This 0.58 difference results in unequal sharing of electrons, contributing to the net dipole moment.
• BeCl2: Beryllium's electronegativity is 1.57, while chlorine's is again 3.16. Although there's a substantial difference of 1.59, the linear geometry leads to the cancellation of dipole moments.

Understanding electronegativity differences can predict whether a molecule exhibits polarity and thus a dipole moment.

SCl2 vs BeCl2

Now, let's dive into the key differences between SCl2 and BeCl2 in terms of their dipole moments and properties.

SCl2: This molecule, due to its bent geometry and significant electronegativity difference between sulfur and chlorine, possesses a distinct dipole moment. The asymmetrical shape ensures that the dipoles do not cancel each other out, resulting in a polar molecule. The net dipole points towards the more electronegative chlorine atoms.

BeCl2: On the other hand, BeCl2 is nonpolar despite having a large electronegativity difference. Its linear geometry causes the dipoles on each side to effectively cancel out, leading to no net dipole moment.

In essence, the combination of geometry and electronegativity differences dictates whether a molecule like SCl2 or BeCl2 has a dipole moment, showcasing the marvelous interplay between these chemical concepts.