Question

Identify the most important types of interparticle forces present in the solids of each of the following substances. a. \(\mathrm{BaSO}_{4}\) e. CsI b. \(\mathrm{H}_{2} \mathrm{~S}\) f. \(\mathrm{P}_{4}\) c. Xe g. \(\mathrm{NH}_{3}\) d. \(\mathrm{C}_{2} \mathrm{H}_{6}\)

Short answer

a. In \(\mathrm{BaSO}_{4}\), the most important interparticle force is ionic bonding. b. In \(\mathrm{H}_{2}\mathrm{S}\), the most important interparticle forces are dipole-dipole interactions. c. In Xe, the most important interparticle forces are London dispersion forces. d. In \(\mathrm{C}_{2}\mathrm{H}_{6}\), the primary interparticle force is London dispersion forces. e. In CsI, the most important interparticle force is ionic bonding. f. In \(\mathrm{P}_{4}\), the primary interparticle forces are London dispersion forces. g. In \(\mathrm{NH}_{3}\), the most important interparticle force is hydrogen bonding.

Step-by-step solution

Substance a: \(\mathrm{BaSO}_{4}\)

We can recognize that \(\mathrm{BaSO}_{4}\) is an ionic compound, since it is composed of a metal (barium) and a polyatomic anion (sulfate). The most important interparticle force in this substance is ionic bonding, which occurs between oppositely charged ions. In this case, barium ion (\(\mathrm{Ba^{2+}}\)) and sulfate ion (\(\mathrm{SO}_{4}^2-\)) are held together by electrostatic forces.

Substance b: \(\mathrm{H}_{2}\mathrm{S}\)

\(\mathrm{H}_{2}\mathrm{S}\) is a covalent molecule, in which two hydrogen atoms and one sulfur atom share electrons to form chemical bonds. The most important interparticle forces in this substance are dipole-dipole interactions due to the polar nature of the covalent bonds between hydrogen and sulfur. This results in a partial positive charge on the hydrogen atoms and a partial negative charge on the sulfur atom, which attract each other.

Substance c: Xe

Xe is a noble gas with a full outer electron shell, which means it exists as individual atoms and does not readily form chemical bonds. The most important interparticle forces in this substance are London dispersion forces, which occur due to temporary fluctuations in electron distribution around the Xe atoms. These fluctuations create temporary dipoles that induce dipoles in neighboring atoms, leading to weak attractive forces.

Substance d: \(\mathrm{C}_{2}\mathrm{H}_{6}\)

\(\mathrm{C}_{2}\mathrm{H}_{6}\), or ethane, is a non-polar covalent molecule formed by carbon and hydrogen atoms sharing electrons. The primary interparticle forces in this substance are London dispersion forces, which arise from temporary fluctuations in electron distribution around the molecule.

Substance e: CsI

CsI is an ionic compound, formed by the combination of a metal (cesium) and a non-metal (iodine). In this substance, the most important interparticle force is ionic bonding, which occurs between the positively charged cesium ion (\(\mathrm{Cs^+}\)) and the negatively charged iodine ion (\(\mathrm{I^-}\)).

Substance f: \(\mathrm{P}_{4}\)

\(\mathrm{P}_{4}\) is a covalent molecule, in which four phosphorus atoms are covalently bonded to form a tetrahedral structure. These covalent bonds involve sharing of electrons between the phosphorus atoms. The primary interparticle forces in this substance are London dispersion forces, as the \(\mathrm{P}_{4}\) molecule is non-polar.

Substance g: \(\mathrm{NH}_{3}\)

\(\mathrm{NH}_{3}\), also known as ammonia, is a covalent molecule featuring one nitrogen atom and three hydrogen atoms. Due to the difference in electronegativity between nitrogen and hydrogen, the molecule is polar, with the nitrogen atom having a partial negative charge and the hydrogen atoms having partial positive charges. Consequently, the most important type of interparticle force in this substance is hydrogen bonding, which occurs between the electronegative nitrogen atom and the partially positively charged hydrogen atoms on neighboring molecules.

Key concepts

Ionic Bonding

Ionic bonding is a powerful type of chemical bond that occurs when electrons are transferred from one atom to another. This transformation typically happens between a metal and a non-metal. As a result, one atom becomes positively charged, while the other becomes negatively charged. This sets the stage for ionic bonding, where the oppositely charged ions are drawn together by strong electrostatic forces.

For example, in the compound barium sulfate, \(\mathrm{BaSO}_4 \), barium (\(\mathrm{Ba^{2+}} \)) and sulfate (\(\mathrm{SO}_4^{2-} \)) ions are bonded together through these ionic forces. You can imagine this bond like powerful magnets clinging together. Ionic bonding is not only found in barium sulfate but is also prevalent in compounds like cesium iodide (\(\mathrm{CsI} \)). In this compound, cesium (\(\mathrm{Cs^+} \)) and iodine (\(\mathrm{I^-} \)) ions form a tough ionic bond.

Dipole-Dipole Interactions

Dipole-dipole interactions are a type of intermolecular force that occurs between polar molecules. These forces are somewhat weaker than ionic bonds but still significant. This happens due to the polar nature of the molecules, where there is an uneven distribution of electron density. Consequently, one end of the molecule becomes slightly positive, while the other end becomes slightly negative.

Take hydrogen sulfide (\(\mathrm{H_2S} \)) as an example. Here, the sulfur atom is more electronegative than the hydrogen atoms, creating a polar molecule. The slight positive charge on the hydrogen atoms is attracted to the slight negative charge on the sulfur atom of another molecule. This attraction is what we call dipole-dipole interactions.

London Dispersion Forces

London dispersion forces are the weakest of all intermolecular forces. However, they are universal to all molecules, whether polar or nonpolar. These forces arise from temporary shifts in electron density, which create fleeting dipoles. These temporary dipoles can induce similar dipoles in neighboring atoms or molecules, leading to an attraction.

For instance, noble gases like xenon (\(\mathrm{Xe} \)) and non-polar molecules such as ethane (\(\mathrm{C_2H_6} \)) and phosphorus (\(\mathrm{P_4} \)) rely on London dispersion forces to hold them together in the solid state. While these forces are weak, when many of them are present, they can add up to have a noticeable effect on the physical properties of a substance.

Covalent Bonds

Covalent bonds are a fundamental type of chemical bond where atoms share electrons rather than transfer them. This sharing creates a strong bond between the atoms, making covalent substances hard to break apart. Covalent bonding commonly occurs between non-metal atoms.

An example is phosphorus (\(\mathrm{P_4} \)), where each phosphorus atom shares electrons with neighboring atoms. Another example is found in ethane (\(\mathrm{C_2H_6} \)), where carbon and hydrogen atoms are tied together via covalent bonds. Covalent bonds are essential in building complex molecular structures and are widely prevalent in organic compounds.

Hydrogen Bonding

Hydrogen bonding is a special type of dipole-dipole interaction that occurs when hydrogen is bound to a highly electronegative atom like nitrogen, oxygen, or fluorine. It's generally stronger than a regular dipole-dipole interaction but weaker than ionic or covalent bonds.

In ammonia (\(\mathrm{NH_3} \)), hydrogen bonding is prevalent. The nitrogen atom's high electronegativity creates a polar molecule. As a result, the partially positive hydrogen atoms attract the partially negative nitrogen in other ammonia molecules. This specific interaction endows ammonia with unique qualities like higher boiling points than similar sized molecules lacking hydrogen bonds.