Animated Solution for Chemistry - Chemical Bonding and Molecular Structure: Which of the following compounds contain(s) no covalent bond(s)? $\text{KCl},{\text{PH}}_3,{\text{O}}_2,{\text{B}}_2{\text{H}}_6,{\text{H}}_2{\text{SO}}_4$

When we dive into the world of chemical bonding, one of the most fundamental skills is distinguishing between the different types of bonds that hold atoms together. The question presents us with a fascinating challenge: we need to identify which of the given compounds—$\text{KCl}$, ${\text{PH}}_3$, ${\text{O}}_2$, ${\text{B}}_2{\text{H}}_6$, or ${\text{H}}_2{\text{SO}}_4$—contains absolutely no covalent bonds.

To tackle this, we must first recall the core definitions. An ionic bond is formed through the complete transfer of one or more electrons from one atom to another. This typically occurs between a metal (which loves to lose electrons) and a non-metal (which loves to gain them), resulting in oppositely charged ions held together by strong electrostatic forces.

On the flip side, a covalent bond is formed when two atoms share pairs of electrons to achieve a stable electron configuration. This sharing almost always happens between two non-metals. Armed with this knowledge, our mission is clear: we are hunting for a compound that is purely ionic, meaning it involves only metals and non-metals transferring electrons, with zero sharing involved.

Let's put each candidate under the microscope, starting with Potassium Chloride ($\text{KCl}$). Potassium ($\text{K}$) is an alkali metal from Group 1, and Chlorine ($\text{Cl}$) is a highly electronegative halogen from Group 17. Potassium eagerly donates its single valence electron to Chlorine. This complete transfer creates a ${\text{K}}^{+}$ cation and a ${\text{Cl}}^{-}$ anion. The bond between them is purely electrostatic. Because there is no sharing of electrons, $\text{KCl}$ contains no covalent bonds.

Next, we look at Phosphine (${\text{PH}}_3$). Both Phosphorus and Hydrogen are non-metals. Phosphorus needs three electrons to complete its octet, so it shares electrons with three Hydrogen atoms, forming three distinct $\text{P-H}$ single covalent bonds. Thus, ${\text{PH}}_3$ is out of the running.

What about the Oxygen molecule (${\text{O}}_2$)? Here, we have two identical Oxygen atoms. Being non-metals, they both need two electrons to achieve stability. They solve this by sharing two pairs of electrons, creating a strong $\text{O=O}$ double covalent bond. Clearly, covalent bonds are present here.

Moving on to Sulfuric Acid (${\text{H}}_2{\text{SO}}_4$), we see a large molecule composed entirely of non-metals: Sulfur, Oxygen, and Hydrogen. The central Sulfur atom shares electrons with four Oxygen atoms, and two of those Oxygen atoms share electrons with Hydrogen atoms. Every single connection in this molecule is a covalent bond.

Finally, let's examine Diborane (${\text{B}}_2{\text{H}}_6$). This molecule is famous for its unique structure. It contains four terminal $\text{B-H}$ bonds, which are standard two-center two-electron covalent bonds. More interestingly, it features two bridging Hydrogen atoms that form three-center two-electron bonds (often called "banana bonds") between the Boron atoms. Despite their exotic nature, these are still formed by electron sharing, making them covalent bonds.

After a thorough analysis, the conclusion is crystal clear. While ${\text{PH}}_3$, ${\text{O}}_2$, ${\text{H}}_2{\text{SO}}_4$, and ${\text{B}}_2{\text{H}}_6$ all rely on the sharing of electrons between non-metals to hold their structures together, Potassium Chloride stands alone.

In $\text{KCl}$, the bond is formed entirely by the complete transfer of an electron from the Potassium atom to the Chlorine atom, resulting in a purely ionic interaction. Therefore, $\text{KCl}$ is the only compound in the list that contains no covalent bonds. This makes option (c) the correct answer.