Question

The size of isoelectronic species - F^-, Ne and Na⁺ is affected by

• A. Nuclear charge (Z )
• B. Valence principal quantum number (n)
• C. Electron-electron interaction in the outer orbitals
• D. None of the factors because their size is the same.

Answer 1

The Correct Option is A

Nuclear Charge (Z): The size of isoelectronic species is primarily affected by their nuclear charge. As the nuclear charge increases, the effective nuclear charge (the net positive charge experienced by electrons) felt by the electrons also increases, pulling them closer to the nucleus. Hence, the size decreases with increasing nuclear charge. In this case, the order of nuclear charge is: \(Z_{\text{Na}^+} = 11\), \(Z_{\text{Ne}} = 10\), and \(Z_{\text{F}^-} = 9\). Therefore, the size order is: F^- > Ne > Na⁺.

1. Valence Principal Quantum Number (n): The principal quantum number primarily determines the energy level in which the electrons are present but does not apply in distinguishing the sizes of isoelectronic species as they all have electrons in the same shell.
2. Electron-Electron Interaction in the Outer Orbitals: Although electron-electron interactions can influence size to some extent, they are not as significant in accounting for the differences in size among isoelectronic species.
3. None of the factors because their size is the same: This is incorrect because as explained, the nuclear charge affects the size significantly, leading to different sizes for these isoelectronic ions.

Based on the above analysis, Nuclear charge (Z) is the correct factor affecting the sizes of isoelectronic species F^-, Ne, and Na⁺.