Question
For each pair, choose the compound with larger lattice energy, and explain your choice.
(a).CaO or CaS.
(b).BaO or SrO.
(a).CaO or CaS.
(b).BaO or SrO.
Answers
GPT-4o mini
To determine which compound in each pair has a larger lattice energy, we need to consider both the charges of the ions involved and the ionic radii of the cations and anions.
**(a) CaO or CaS:**
- **Ionic Charges:** Both CaO and CaS consist of calcium ions (Ca²⁺) and O²⁻ or S²⁻, respectively. The charges of the ions in both compounds are the same (2+ for Ca and 2- for O and S).
- **Ionic Radii:** However, we need to consider the relative sizes of the oxide ions (O²⁻) and sulfide ions (S²⁻). Oxygen is smaller than sulfur, meaning that O²⁻ has a smaller ionic radius than S²⁻.
Based on these factors, the lattice energy is higher for CaO because the smaller radius of the O²⁻ ions allows for stronger electrostatic interactions between the Ca²⁺ and O²⁻ ions compared to the interactions between Ca²⁺ and S²⁻ in CaS. Therefore, **CaO has larger lattice energy than CaS.**
**(b) BaO or SrO:**
- **Ionic Charges:** Both BaO and SrO consist of barium ions (Ba²⁺) and oxide ions (O²⁻). The charge of the ions is the same in both compounds (2+ for Ba and 2- for O).
- **Ionic Radii:** However, we need to consider the size of the cations; Ba²⁺ is larger than Sr²⁺ because barium is below strontium in the periodic table, which means that it has a larger ionic radius.
Since the lattice energy is inversely proportional to the distance between the ions, the smaller SR²⁺ ion will result in a stronger electrostatic attraction with the O²⁻ ion compared to the larger Ba²⁺. Thus, **SrO has larger lattice energy than BaO.**
In summary:
(a) CaO has larger lattice energy than CaS.
(b) SrO has larger lattice energy than BaO.
**(a) CaO or CaS:**
- **Ionic Charges:** Both CaO and CaS consist of calcium ions (Ca²⁺) and O²⁻ or S²⁻, respectively. The charges of the ions in both compounds are the same (2+ for Ca and 2- for O and S).
- **Ionic Radii:** However, we need to consider the relative sizes of the oxide ions (O²⁻) and sulfide ions (S²⁻). Oxygen is smaller than sulfur, meaning that O²⁻ has a smaller ionic radius than S²⁻.
Based on these factors, the lattice energy is higher for CaO because the smaller radius of the O²⁻ ions allows for stronger electrostatic interactions between the Ca²⁺ and O²⁻ ions compared to the interactions between Ca²⁺ and S²⁻ in CaS. Therefore, **CaO has larger lattice energy than CaS.**
**(b) BaO or SrO:**
- **Ionic Charges:** Both BaO and SrO consist of barium ions (Ba²⁺) and oxide ions (O²⁻). The charge of the ions is the same in both compounds (2+ for Ba and 2- for O).
- **Ionic Radii:** However, we need to consider the size of the cations; Ba²⁺ is larger than Sr²⁺ because barium is below strontium in the periodic table, which means that it has a larger ionic radius.
Since the lattice energy is inversely proportional to the distance between the ions, the smaller SR²⁺ ion will result in a stronger electrostatic attraction with the O²⁻ ion compared to the larger Ba²⁺. Thus, **SrO has larger lattice energy than BaO.**
In summary:
(a) CaO has larger lattice energy than CaS.
(b) SrO has larger lattice energy than BaO.