Question

Which of the following orders of ionic radii is correctly represented?

• A. \(Na^+ > F^- > O^{2-}\)
• B. \(O^{2-}>F^->Na^+\)
• C. \(Al^{3+}>Mg^{2+}>N^{3-}\)
• D. \(H^->H^+>H\)

Answer 1

The Correct Option is B

 To determine the correct order of ionic radii among the given options, let's first understand the concept of ionic radii and compare ions based on their size:

1. Concept of Ionic Radii:
   • The ionic radius of an ion is a measure of its size, which varies due to the gain or loss of electrons during ion formation.
   • Anions (negatively charged ions) are generally larger than their parent atoms because the addition of electrons increases repulsion among electrons, leading to an expansion of the electron cloud.
   • Cations (positively charged ions) are smaller than their parent atoms because the loss of electrons reduces electron-electron repulsion, allowing the electron cloud to contract closer to the nucleus.
2. Comparing Ionic Radii:
   • \(Na^+\) has lost one electron, resulting in a smaller radius than both \(F^-\) and \(O^{2-}\).
   • \(F^-\): Gained one electron, so it is larger than \(Na^+\) and smaller than \(O^{2-}\).
   • \(O^{2-}\): Gained two electrons, making it the largest among the three.
3. Correct Order of Ionic Radii:
   • Therefore, the order for the ionic radii from largest to smallest is \(O^{2-} > F^- > Na^+\).

Conclusion: The correct order is \(O^{2-} > F^- > Na^+\), which corresponds to the second option.