Question

Write the letter(s) corresponding to the bond(s) and/or force(s) associated with each species below. A - dispersion forces \(\mathrm{B}-\) dipole-dipole interaction C - ionic bond \(\mathrm{D}-\) metallic bond \(\mathrm{E}-\) covalent bond within a network covalent solid \(\mathrm{F}\) - hydrogen bond. (a) C (diamond) (b) \(\mathrm{CH}_{3}\) (c) \(\mathrm{Au}\) (d) \(\mathrm{SO}_{3}\) (e) \(\mathrm{NH}_{3}\) (f) \(\mathrm{KCl}\)

Short answer

Question: Identify the type of intermolecular interactions or bonds associated with each of the following chemical species: (a) C (diamond), (b) CH3, (c) Au, (d) SO3, (e) NH3, and (f) KCl. Answer: (a) Diamond is associated with covalent bond within a network covalent solid. (b) CH3 is associated with dispersion forces. (c) Au is associated with a metallic bond. (d) SO3 is associated with dipole-dipole interaction. (e) NH3 is associated with hydrogen bonds. (f) KCl is associated with ionic bonds.

Step-by-step solution

(a) C (diamond)

Diamond is made up of carbon atoms that are covalently bonded within a network. This makes it a network covalent solid. Therefore, the force associated with diamond is E - covalent bond within a network covalent solid.

(b) CH3

CH3 or methyl group is a component of larger organic compounds; however, for the purpose of this exercise, we can treat it as a standalone species. It consists of a carbon atom bonded to three hydrogen atoms. Although it is a polar molecule, the methyl group has a temporary dipole when electrons move unevenly around the carbon and hydrogen atoms, leading to Dispersion forces (London forces). Thus, the force associated with the CH3 group is A - dispersion forces.

(c) Au

Au (gold) is a metal, and it forms a metallic bond with other gold atoms in a gold lattice. The metallic bond results from the electrostatic attractive force between conduction electrons and positively charged metal ions. So, the bond associated with Au is D - metallic bond.

(d) SO3

SO3 (sulfur trioxide) is a covalent molecule, and it forms polar covalent bonds within the molecule. As a result, there will be a permanent dipole between the sulfur and oxygen atoms, leading to dipole-dipole interactions between different SO3 molecules. Thus, the force associated with SO3 is B - dipole-dipole interaction.

(e) NH3

NH3 (ammonia) is a molecule that has nitrogen bonded to three hydrogen atoms. NH3 is well-known for its ability to form hydrogen bonds between ammonia molecules. These hydrogen bonds occur when the nitrogen atom, which is electronegative, attracts the hydrogen atom of a neighboring NH3 molecule. So, the force associated with NH3 is F - hydrogen bond.

(f) KCl

KCl (potassium chloride) is an ionic compound formed by the transfer of an electron from potassium to chlorine. This transfer results in the formation of a positive potassium ion and a negative chloride ion that attracts each other due to their opposite charge. The interaction between these ions leads to an ionic bond. Therefore, the bond associated with KCl is C - ionic bond.

Key concepts

Dispersion Forces

When learning about chemical bonding, it's important to start with the basics. Dispersion forces, also known as London forces, are the weakest type of intermolecular attractions. Yet, they are present in all molecules, whether polar or nonpolar. These forces arise due to temporary fluctuations in the electron distribution within molecules, which leads to a temporary dipole. When molecules come close enough, these temporary dipoles induce a dipole in the neighboring molecules, leading to an attraction between them.

For instance, in hydrocarbons and noble gases, dispersion forces are the only type of intermolecular forces present. They are crucial for understanding why nonpolar molecules still exhibit physical properties like boiling and melting points. The strength of dispersion forces increases with the size of the molecules or atoms and with increasing surface area.

Dipole-Dipole Interaction

Moving a step further in complexity, we have dipole-dipole interactions. These occur between molecules that have permanent dipoles, which means that there is an uneven distribution of electron density within the molecule. One end of the molecule has a partial negative charge, while the other end has a partial positive charge.

These positive and negative charges attract each other, leading to an intermolecular force known as dipole-dipole interaction. Molecules with strong dipole-dipole interactions tend to have higher boiling points compared to similar sized molecules that do not have these interactions. The classic example is water, where the oxygen is partially negative, and the hydrogens are partially positive, resulting in a polar molecule that has a high boiling point due to strong dipole-dipole interactions.

Ionic Bond

An ionic bond is more like a commitment than a casual date; it's a strong bond formed between two oppositely charged ions. This type of bond typically occurs when a metal atom transfers one or more of its electrons to a nonmetal atom. This electron transfer creates a cation (a positively charged ion) and an anion (a negatively charged ion).

The electrostatic attraction between these oppositely charged ions forms the ionic bond, which is essentially the glue that holds the ions together in a lattice structure. This structure contributes to the high melting and boiling points of ionic compounds, making them solid at room temperature. Common table salt, or sodium chloride (NaCl), is a perfect example of an ionic compound.

Metallic Bond

The metallic bond is what gives metals their unique properties, such as malleability, ductility, and excellent conductivity of heat and electricity. Unlike ionic or covalent bonds, metallic bonding involves a 'sea' of delocalized electrons. These electrons are not bound to any one atom but move freely around the metal's lattice of positively charged ions.

Think of a metallic bond as a communal sharing of electrons. This sharing allows metals to be hammered into sheets (malleable) or drawn into wires (ductile) without breaking. The conductivity of metals is a direct result of these free-flowing electrons, as they can easily transfer energy throughout the metal.

Covalent Bond

A covalent bond is formed when atoms share pairs of electrons. This sharing allows each atom to achieve a full outer shell of electrons, which brings stability, making covalent bonds a stable chemical connection. Molecules formed by covalent bonds can be simple, like the oxygen we breathe (O2), or very complex, like the DNA in our cells.

What's fascinating about covalent bonds is that they can form between atoms of the same element or between different elements. This versatility leads to the creation of an incredible variety of molecules. Covalent bonds can be single, with one pair of shared electrons; double, with two pairs; or even triple, with three pairs of shared electrons.

Hydrogen Bond

Hydrogen bonds are special types of dipole-dipole interactions and are exceptionally important in biological molecules. These bonds occur when a hydrogen atom is covalently bonded to a highly electronegative atom such as nitrogen, oxygen, or fluorine. The electronegative atom pulls the electron density away from the hydrogen, exposing the hydrogen's nucleus and creating a strong partial positive charge.

This partial positive charge can then interact with a lone pair of electrons on another electronegative atom, forming a hydrogen bond. Hydrogen bonds are much stronger than regular dipole-dipole interactions but weaker than covalent or ionic bonds. They are responsible for many of the unique properties of water, as well as the complex structures of proteins and DNA in our cells.