Which of the following factors are required for element substitution? (Choose all that apply. Wrong answers will be penalized.)

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BlackTom AI · Accepted Answer

The question asks which factors are required for element substitution, and it indicates this is a choose-all-that-apply scenario with penalties for wrong answers. However, the provided data shows no answer options to evaluate. I will nonetheless discuss the factors commonly considered essential for substitution in solid-state chemistry and highlight how the two factors you listed align with that concept.

General concept: for an atom or ion to substitute another in a crystal lattice, it must fit into the lattice site without causing excessive strain or charge imbalance. Two primary structural/chemical requirements often cited are: (a) similar ionic radius (size compatibility) and (b) compatible valence or charge (to maintain overall charge neutrality and proper electrostatic environment).

Option analysis (hypothetical options based on common knowledge):
- Same valence charge: If the substituting ion has the same valence as the ion it replaces, the substitution is more likely to preserve the overall charge balance of the crystal, reducing the need for additional lattice defects or compensating defects. This helps maintain electrical neutrality and preserves the crystal’s stoichiometry. Misconception to avoid: substituting with a different charge can sometimes be tolerated if the crystal structure can accommodate charge compensation mechanisms, but it often requires defects or vacancies to balance charge, which can destabilize the lattice.
- Similar ionic radius: Size compatibility minimizes lattice strain. If the substituting ion is too large or too small, it distorts the crystal lattice, raises the system’s energy, and can disrupt properties. However, exact similarity is not always strictly necessary—some lattices tolerate a range of sizes via elastic accommodation or by creating defects—but in most typical substitution scenarios, closer ionic radii are favored.

Notes on common reasons other factors matter (helpful to understand why other potential options would be incorrect):
- Different valence without compensation: Substituting a ion with a different charge without compensating defects would create a net charge imbalance, which is generally unfavorable in a perfect lattice.
- Significantly different ionic radius: Severe size mismatch increases lattice strain, often lowering stability or changing properties like band structure, diffusion, or solubility limits.
- Coordination number mismatch: If the substituting ion cannot adopt the same coordination environment as the site it replaces, the substitution becomes unfavorable even if charge and size are similar.
- Electronic structure and preferred oxidation state: Beyond size and charge, the chemistry of the element (like preferred oxidation state and bonding tendencies) can affect whether substitution is feasible.

Given the standard framework for substitution, the two factors you listed—same valence charge and similar ionic radius—are the core criteria most commonly cited as required or highly favorable for substitution, with the caveat that real systems may tolerate deviations under certain conditions if compensating mechanisms are present.

EOSC_V 118 99C 2024W2 测验 1 (L2-7)

Which of the following factors are required for element substitution? (Choose all that apply. Wrong answers will be penalized.)

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