Which of the following is the least ionic?
1. AgCl
2. CoCl2
3. KCl
4. BaCl2
The correct answer and explanation is:
The correct answer is CoCl2.
Explanation:
To understand which compound is the least ionic, we need to consider the nature of the bond between the elements in each compound. Ionic bonds occur when electrons are transferred from one atom to another, resulting in the formation of positively charged cations and negatively charged anions. The ionic character depends on the difference in electronegativity between the two atoms involved. A larger difference leads to a more ionic bond. However, other factors such as the size of the ions and the polarizability also play significant roles in determining the bond’s ionic nature.
- AgCl (Silver chloride):
- Silver (Ag) is a transition metal with a relatively low electronegativity compared to chlorine. However, silver’s ionic radius is large, and it can polarize the chloride ion due to its relatively high charge-to-radius ratio. The bond in AgCl is ionic, but it has some degree of covalent character due to silver’s ability to polarize the chloride ion.
- CoCl2 (Cobalt(II) chloride):
- Cobalt (Co) is also a transition metal. The ionic bond in CoCl2 is weaker than in the other compounds listed because cobalt has a relatively low charge-to-radius ratio compared to alkali metals like potassium or barium. This means that cobalt does not strongly attract chloride ions in a typical ionic fashion, leading to less ionic character and more covalent character in the bonding. Cobalt is more likely to share electrons, making this compound less ionic.
- KCl (Potassium chloride):
- Potassium (K) is an alkali metal with a low electronegativity. Potassium chloride is highly ionic because of the large difference in electronegativity between potassium and chlorine. Potassium readily loses an electron, forming a K+ cation, while chlorine gains an electron to form the Cl- anion.
- BaCl2 (Barium chloride):
- Barium (Ba) is an alkaline earth metal, and like potassium, it has a relatively low electronegativity compared to chlorine. The ionic bond in BaCl2 is quite strong because barium, with its larger ionic size and two positive charges, forms a highly ionic bond with chloride.
Comparing these compounds, CoCl2 is the least ionic because the cobalt ion does not produce as strong an electrostatic attraction with the chloride ions, leading to a bond with more covalent character than the other compounds. The other compounds, particularly KCl and BaCl2, exhibit stronger ionic bonds due to the larger charge-to-radius ratios of potassium and barium.