Ionic Bonding: Videos & Practice Problems

Chemical bonding is the attractive force that holds atoms or ions together in a chemical compound, allowing elements to either share or transfer electrons to achieve a filled outer shell, similar to noble gases. When focusing on ionic bonding, it is essential to understand that ionic compounds, also known as ionic salts, consist of a positive ion (cation) and a negative ion (anion). The attractive force between these oppositely charged ions is what forms the ionic compound.

In ionic bonding, metals typically lose their valence electrons, resulting in a positive charge, while nonmetals gain electrons, leading to a negative charge. This transfer of electrons lowers the potential energy of the ions involved. For instance, sodium (Na), which is in Group 1A, loses an electron to become Na⁺. Conversely, chlorine (Cl), found in Group 7A, gains that electron, resulting in Cl^-. The combination of these ions, due to their opposing charges, forms sodium chloride (NaCl), a classic example of an ionic compound.

It is also important to differentiate ionic compounds from covalent compounds, which consist solely of nonmetals and involve the sharing of electrons rather than the transfer. However, the fundamental principle of ionic compounds remains the attraction between cations and anions, driven by their opposite charges, which is crucial for the formation of ionic solids.

When evaluating which species exhibits the most ionic character, it is essential to understand the nature of ionic bonding. Ionic bonds form between a cation, typically a metal or the ammonium ion, and an anion, which is usually a nonmetal. This fundamental definition distinguishes ionic compounds from covalent compounds, where nonmetals bond with each other.

The ionic character of a bond increases when there is a significant difference in electronegativity between the cation and anion. In this context, we are looking for a combination of a metal and a nonmetal, as this pairing is characteristic of ionic compounds. Among the options provided, the correct choice is option C, which features tin (Sn), a metal, bonded to oxygen (O), a nonmetal. This pairing exemplifies the criteria for ionic bonding, as it consists of a metal connected to a nonmetal.

In contrast, the other options consist solely of nonmetals bonded together, which would classify them as covalent compounds rather than ionic. Therefore, recognizing the metal-to-nonmetal connection is crucial in identifying the species with the most ionic character.

Ionic compounds exhibit distinct properties that are influenced by the strength of the attractive forces between their opposing ions. These properties include physical state, conductivity, temperature characteristics, and durability.

At room temperature, ionic compounds typically exist as solids due to the strong electrostatic forces between positively charged cations and negatively charged anions. This attraction results in a rigid lattice structure, contributing to their solid state.

When dissolved in a solvent such as water, ionic compounds become good electrical conductors. This is because the ions are free to move in solution, allowing them to carry an electric current. In contrast, ionic solids do not conduct electricity in their solid form, as the ions are fixed in place within the lattice.

Ionic compounds are characterized by high melting and boiling points. The strong ionic bonds require significant energy to break, which is why these compounds remain solid at elevated temperatures. This property is essential in various applications where heat resistance is necessary.

In terms of mechanical properties, ionic solids are hard due to their strong ionic bonds. However, they are also brittle; when subjected to stress, such as being struck with a hammer, they tend to splinter and crack. This brittleness arises from the alignment of like charges when the lattice is distorted, leading to repulsion and fracture.

In summary, the properties of ionic compounds—solid state at room temperature, conductivity when dissolved, high melting and boiling points, and a combination of hardness and brittleness—are all a direct result of the strong electrostatic attractions between their constituent ions.

To determine which compound has properties most similar to sodium chloride (NaCl), we first recognize that sodium chloride is an ionic compound formed from a metal (sodium) and a nonmetal (chlorine). In this compound, sodium exists as a cation (Na⁺) and chlorine as an anion (Cl^-), with their opposing charges leading to the formation of the ionic bond.

When evaluating other compounds, it is essential to identify those that also consist of a metal and a nonmetal, as these will likely exhibit similar ionic properties. Among the options provided, compounds that are composed solely of nonmetals are classified as covalent compounds, which differ significantly from ionic compounds in terms of bonding and properties.

In this context, potassium bromide (KBr) stands out as the most similar compound to sodium chloride. Like NaCl, potassium bromide is formed from a metal (potassium) and a nonmetal (bromine), resulting in the formation of an ionic bond. Therefore, KBr shares similar properties with NaCl, such as high melting and boiling points, electrical conductivity in molten or dissolved states, and solubility in water.

In conclusion, potassium bromide (KBr) is the correct answer, as it is an ionic compound composed of a metal and a nonmetal, mirroring the structure and properties of sodium chloride.