Question

Favourable conditions for ionic bond are (1) low charge on ions, large cation and small anion (2) high charge on ions, small cation and large anion (3) high charge on ions, large cation and small anion (4) low charge on ions, small cation and large anion

Short answer

Option (1) low charge on ions, large cation and small anion.

Step-by-step solution

Analyze the Role of Charge

Ionic bonds form when one atom donates an electron to another atom, creating positive and negative ions. Lower charge on the ions is favorable because higher charges can cause strong repulsion between ions, making the structure less stable.

Evaluate the Size of the Cation

A larger cation is preferable because it can distribute its positive charge over a larger volume, reducing the energy associated with the ionic bond formation.

Evaluate the Size of the Anion

A smaller anion is preferable because it can hold its negative charge tightly, making the ionic bond stronger and the compound more stable.

Combine the Favorable Conditions

Combine the conclusions from the previous steps. The favorable conditions for an ionic bond are low charge on ions, a large cation, and a small anion.

Match with Given Options

Compare the combined favorable conditions with the given options. (1) low charge on ions, large cation and small anion matches the favorable conditions.

Key concepts

Ionic Bonds

Ionic bonds are a type of chemical bond formed between two atoms when one atom donates an electron to another. This causes one atom to become positively charged (cation) and the other to become negatively charged (anion). The electrostatic attraction between these opposite charges holds the atoms together. Ionic bonds are typically formed between metals and non-metals. The strength of the ionic bond depends largely on several factors such as the charge of the ions, the size of the cation, and the size of the anion.

Understanding these factors helps us comprehend why certain combinations of elements form stronger ionic bonds than others.

Cation Size

A cation is an ion with a positive charge. The size of the cation plays an important role in the formation and stability of an ionic bond. Larger cations are generally preferable in forming ionic bonds due to some key reasons:

• A larger cation can distribute its positive charge over a larger volume. This reduces the electrostatic potential energy and makes the resulting ionic compound more stable.
• Since the positive charge is spread over a greater area, the overall repulsive forces between the ions are minimized, contributing to the stability of the ionic structure.

Examples of large cations include alkaline earth metals like calcium (Ca²⁺) and magnesium (Mg²⁺), which effectively form strong ionic bonds with smaller anions.

Anion Size

An anion is an ion with a negative charge. The size of the anion is also crucial in determining the strength and stability of an ionic bond. Smaller anions are generally more favorable for several reasons:

• A smaller anion holds its negative charge more tightly, reducing the repulsive forces between the ions and thus making the bond stronger.
• It can more effectively attract and maintain a stable bond with the cation, contributing to the overall stability of the ionic compound.

Common examples of small anions include halogens like fluoride (F^-) and chloride (Cl^-), which form strong ionic bonds due to their small size and strong negative charges.

Ion Charge

The charge of the ions involved in forming an ionic bond significantly influences the bond's strength and stability. Here’s why:

• Lower charge on the ions is generally more favorable. Higher charges can result in strong electrostatic repulsion between the ions, making the structure less stable.
• Lower charged ions tend to form more stable and less reactive compounds because the overall energy required to maintain the bond is lower compared to highly charged ions.

An example would be sodium chloride (NaCl), where sodium (Na⁺) and chloride (Cl^-) ions have low charges and form very stable ionic bonds.