Question

Consider the two ionic compounds NaCl and CaO. In which compound are the cation-anion attractive forces stronger? Explain your answer.

Short answer

CaO has stronger cation-anion attractive forces than NaCl due to its ions with higher charges.

Step-by-step solution

Identify the Ions

Identify the ions present in each compound. In NaCl (Sodium Chloride), the ions are sodium (Na⁺) and chloride (Cl⁻). In CaO (Calcium Oxide), the ions are calcium (Ca²⁺) and oxide (O²⁻).

Understand Charge Impact

The strength of ionic bonds is greatly influenced by the charge of the ions. Generally, the greater the charge on the ions, the stronger the ionic bond will be. In NaCl, the ions carry charges of +1 and -1 (Na⁺ and Cl⁻). In CaO, the ions carry charges of +2 and -2 (Ca²⁺ and O²⁻).

Compare Ionic Charges

Compare the charges of the ions in both compounds. NaCl: The charges are +1 and -1. CaO: The charges are +2 and -2. Since CaO has ions with greater charges, its ionic bonds are stronger than those in NaCl.

Apply Coulomb's Law

According to Coulomb's Law, the force of attraction between two oppositely charged ions is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. The larger the product of the ion charges, the stronger the force of attraction. Hence, the Ca²⁺ and O²⁻ ions will experience a stronger attractive force compared to the Na⁺ and Cl⁻ ions due to their higher charges.

Key concepts

Cation-Anion Interaction

In ionic compounds, the cation-anion interaction is the foundation of ionic bonding. This type of interaction occurs between positively charged ions called cations and negatively charged ions known as anions.

• The cations and anions are held together by electrostatic forces of attraction.
• This bond forms the ionic lattice in solid-state compounds.

Ions will arrange themselves in a manner that maximizes the attraction between differently charged ions while minimizing the repulsion between ions of the same charge. In sodium chloride (NaCl), sodium (Na⁺) acts as the cation and chloride (Cl⁻) as the anion. In calcium oxide (CaO), calcium (Ca²⁺) is the cation, and oxide (O²⁻) is the anion. These interactions are essential because they determine the physical properties of the compound, such as melting and boiling points, hardness, and solubility. Greater cation-anion attraction typically means a more stable compound.

Coulomb's Law

Coulomb's Law is fundamental to understanding ionic bonding and the strength of the electrostatic interactions between ions. It provides a way to calculate the force (\[ F \] ) of interaction between two charges. According to Coulomb's Law:\[ F = k \frac{{|q_1 \, q_2|}}{{r^2}} \] * Here, \( F \) is the force of attraction or repulsion. * \( k \) is Coulomb's constant. * \( q_1 \) and \( q_2 \) are the magnitudes of the charges involved. * \( r \) is the distance between the centers of the two charges.The implication is that the larger the product of the charges \( q_1 \) and \( q_2 \), the stronger the force of attraction between the ions. Additionally, the closer the ions are to each other, the stronger the attraction. In the case of CaO versus NaCl, CaO has a higher product of charges (\(+2\) and \(-2\)) compared to NaCl (\(+1\) and \(-1\)), resulting in a stronger bond strength as predicted by Coulomb's Law.

Charge of Ions

The charge of ions plays a crucial role in determining the strength of ionic bonds.

• Cations have a positive charge, having lost electrons.
• Anions have a negative charge, having gained electrons.

The magnitude of these charges directly influences the force of attraction in an ionic bond. In the comparison of NaCl and CaO, we focus on the charges of the ions involved. For NaCl: * Sodium (Na⁺) has a charge of +1. * Chloride (Cl⁻) has a charge of -1. For CaO: * Calcium (Ca²⁺) has a charge of +2. * Oxide (O²⁻) has a charge of -2. The ions in CaO have higher charges than those in NaCl, leading to stronger attractive forces between calcium and oxide ions. Thus, the higher the ionic charges, the stronger the electrostatic attraction, making CaO bonds stronger than those in NaCl.