Question

A chemist possesses \(\mathrm{KCl}, \mathrm{PH}_{3}, \mathrm{GeCl}_{4}, \mathrm{H}_{2} \mathrm{~S}\), and \(\mathrm{Cs} \mathrm{F}\). Which of these compounds do not contain a covalent bond?

Short answer

The compounds \(\mathrm{KCl}\) and \(\mathrm{CsF}\) do not contain covalent bonds, as they are ionic compounds formed by the transfer of electrons between their constituent atoms.

Step-by-step solution

Identify KCl

Potassium chloride (\(\mathrm{KCl}\)) is an ionic compound formed by the transfer of an electron from potassium (\(\mathrm{K}\)) to chlorine (\(\mathrm{Cl}\)). The metal, potassium, donates an electron, while the nonmetal, chlorine, accepts the electron. Therefore, there are no covalent bonds in \(\mathrm{KCl}\).

Identify PH3

Phosphine (\(\mathrm{PH}_{3}\)) is a covalent compound formed by the sharing of electrons between phosphorus (\(\mathrm{P}\)) and hydrogen (\(\mathrm{H}\)). Both are nonmetals, and they share electron pairs to form covalent bonds. Therefore, \(\mathrm{PH}_{3}\) does contain covalent bonds.

Identify GeCl4

Germanium tetrachloride (\(\mathrm{GeCl}_{4}\)) is a covalent compound formed by the sharing of electrons between germanium (\(\mathrm{Ge}\)) and chlorine (\(\mathrm{Cl}\)). Both are nonmetals, and they share electron pairs to form covalent bonds. Therefore, \(\mathrm{GeCl}_{4}\) does contain covalent bonds.

Identify H2S

Hydrogen sulfide (\(\mathrm{H}_{2} \mathrm{S}\)) is a covalent compound formed by the sharing of electrons between hydrogen (\(\mathrm{H}\)) and sulfur (\(\mathrm{S}\)). Both are nonmetals, and they share electron pairs to form covalent bonds. Therefore, \(\mathrm{H}_{2} \mathrm{S}\) does contain covalent bonds.

Identify CsF

Cesium fluoride (\(\mathrm{CsF}\)) is an ionic compound formed by the transfer of an electron from cesium (\(\mathrm{Cs}\)) to fluorine (\(\mathrm{F}\)). The metal, cesium, donates an electron, while the nonmetal, fluorine, accepts the electron. Therefore, there are no covalent bonds in \(\mathrm{CsF}\).

Conclusion

The compounds \(\mathrm{KCl}\) and \(\mathrm{CsF}\) do not contain covalent bonds.

Key concepts

Ionic Compounds

Ionic compounds are formed when a metal and a nonmetal exchange electrons. The metal donates one or more electrons to become positively charged, while the nonmetal accepts those electrons to become negatively charged. This transfer creates a strong electrostatic attraction between the opposite charges, thus forming an ionic bond.

Key characteristics of ionic compounds include:

• High melting and boiling points due to strong attractions between ions.
• They are typically solid at room temperature.
• When dissolved in water, ionic compounds often conduct electricity due to the movement of ions.

In the exercise, potassium chloride ( KCl) and cesium fluoride ( CsF) are identified as ionic compounds. These compounds result from the transfer of an electron from a metal (potassium or cesium) to a nonmetal (chlorine or fluorine). As a result, they lack covalent bonds.

Electron Sharing

Electron sharing is fundamental to covalent bonding. Unlike ionic bonds that form from the transfer of electrons, covalent bonds arise when two atoms, typically nonmetals, share pairs of electrons. This sharing allows each atom to attain a stable electron configuration, often resembling the nearest noble gas.

Some essential points about electron sharing include:

• Electron sharing leads to the formation of molecules.
• Covalent bonds can be single, double, or triple, depending on the number of electron pairs shared.
• Nonmetals exhibit high electronegativities, thus tending to gain or share electrons to achieve stability.

In the solution, examples of compounds with electron sharing include PH_b3, GeCl_b4, and H_b2S, where the atoms involved share electrons to form covalent bonds.

Bond Types

In chemistry, understanding bond types is essential to predict the behavior and properties of compounds. Bonds in compounds are primarily classified as ionic or covalent.

• Ionic Bonds: Formed through an electron transfer between a metal and a nonmetal, resulting in oppositely charged ions.
• Covalent Bonds: Result from electron sharing between nonmetal atoms, such as in molecular compounds.

The distinction between ionic and covalent bonds can often predict the properties of the compound, such as electrical conductivity, solubility, and melting points. Understanding whether a compound is ionic or covalent helps in determining its practical applications and reactions in different environments.

Potassium Chloride

Potassium chloride ( KCl) is a classic example of an ionic compound. Composed of potassium (K) and chlorine (Cl), KCl forms through the transfer of an electron from potassium to chlorine.

In this process:

• Potassium loses an electron to become a positively charged ion ( K^ +).
• Chlorine gains an electron to become a negatively charged ion ( Cl^ -).

The resulting electrostatic attraction between potassium and chlorine ions creates a strong ionic bond. KCl is used in various applications, such as:

• As a salt substitute in food.
• In medicine as an electrolyte replenisher.
• In agriculture as a fertilizer component.

Due to its ionic nature, potassium chloride is soluble in water and conducts electricity when dissolved or melted.