Question

Which of the following are ionic compounds and which are covalent compounds: \(\mathrm{RbCl}, \mathrm{PF}_{5}, \mathrm{BrF}_{3}, \mathrm{KO}_{2}, \mathrm{CI}_{4} ?\)

Short answer

RbCl and KO2 are ionic; PF5, BrF3, and CI4 are covalent.

Step-by-step solution

Identify the Elements

The first step is to determine the types of elements present in each compound. Elements can be metals, nonmetals, or metalloids. Typically, ionic compounds form between metals and nonmetals, while covalent compounds form between nonmetals or metalloids.

Analyze \\(\mathrm{RbCl}\\)

Rubidium (Rb) is a metal and chlorine (Cl) is a nonmetal. The presence of a metal and a nonmetal suggests that \(\mathrm{RbCl}\) is an ionic compound.

Analyze \\(\mathrm{PF}_{5}\\)

Phosphorus (P) and fluorine (F) are both nonmetals. Covalent bonds usually form between nonmetals. Therefore, \(\mathrm{PF}_{5}\) is a covalent compound.

Analyze \\(\mathrm{BrF}_{3}\\)

Bromine (Br) and fluorine (F) are both nonmetals. The bonding between nonmetals indicates that \(\mathrm{BrF}_{3}\) is a covalent compound.

Analyze \\(\mathrm{KO}_{2}\\)

Potassium (K) is a metal, and oxygen (O) is a nonmetal. The combination of a metal and a nonmetal suggests \(\mathrm{KO}_{2}\) is an ionic compound.

Analyze \\(\mathrm{CI}_{4}\\)

Carbon (C) and iodine (I) are both nonmetals. Since covalent bonds form between nonmetals, \(\mathrm{CI}_{4}\) is a covalent compound.

Key concepts

Chemical Bonding

Chemical bonding refers to the process where atoms combine to form compounds. These bonds are the forces that hold atoms together. There are several types of chemical bonds, but the most common ones are ionic and covalent bonds. Understanding the nature of these bonds helps in predicting the properties of the compound formed. When atoms bond, they either share or transfer electrons. This process aims to achieve a stable electron configuration. Typically, this means achieving a full outer electron shell, similar to the electron configuration of noble gases. The type of bond formed depends on the elements involved:

• Ionic bonds generally form when a metal and a nonmetal chemically combine.
• Covalent bonds occur when two nonmetals or metalloids share electrons.

Metal and Nonmetal

Metals and nonmetals are two broad categories of elements with distinct characteristics. Understanding these will help in predicting the type of compound they will form. Metals are typically located on the left side of the periodic table. They tend to lose electrons easily to form positive ions, known as cations. This is primarily due to their lower electronegativity and ionization energies. Nonmetals, on the other hand, are found on the right side of the periodic table. These elements have higher electronegativity and prefer to gain electrons to form negative ions, called anions. When metals and nonmetals react, they form ionic compounds due to the transfer of electrons. This results in strong attractions between oppositely charged ions.

Covalent Bonds

Covalent bonds involve the sharing of electron pairs between atoms. These bonds typically form between nonmetals or metalloids. Each atom contributes one or more electrons to the shared pair, leading to strong bonds that hold the atoms together in a molecule. The bond strength and properties of a covalent compound depend on:

• The number of shared electron pairs, which can be single, double, or triple bonds.
• The nature of the atoms involved, such as their electronegativity differences.
• Geometric arrangements, which can affect the compound's shape and properties.

For example, molecules like ext{PF}_5 and ext{BrF}_3 are covalent because both involve nonmetals sharing electrons evenly with different atoms.

Ionic Bonds

Ionic bonds are formed through the transfer of electrons from one atom to another, resulting in the formation of ions. These bonds typically occur between metals and nonmetals. The metal atom loses electrons to become a positively charged cation, while the nonmetal gains these electrons to become a negatively charged anion. This electron exchange leads to a strong electrostatic attraction between the oppositely charged ions, forming an ionic compound. Characteristics of ionic compounds include high melting points, electrical conductivity when dissolved in water, and crystalline structures. Examples of ionic compounds include ext{RbCl} and ext{KO}_2, where metals such as rubidium and potassium interact with nonmetals like chlorine and oxygen respectively to form stable ionic bonds.