Arrange the following isoelectronic series in order of decreasing radius: F^–, O^2–, Mg²⁺, Na⁺.

• A. O^2- > F^- > Na⁺ > Mg²⁺
• B. F^- > O^2- > Na⁺ > Mg²⁺
• C. O^2- > F^- > Mg²⁺ > Na⁺
• D. F^- > O^2- > Mg²⁺ > Na⁺
• E. O^2- > Na⁺ > F^- > Mg²⁺

Answer: (A)

Verified step by step guidance

1. Identify that the species are isoelectronic, meaning they have the same number of electrons. In this case, each species has 10 electrons.
2. Recognize that the size of an ion in an isoelectronic series is determined by the nuclear charge, which is the number of protons in the nucleus.
3. Understand that a higher nuclear charge pulls the electron cloud closer to the nucleus, resulting in a smaller ionic radius.
4. List the species with their respective nuclear charges: O2- (8 protons), F- (9 protons), Na+ (11 protons), Mg2+ (12 protons).
5. Arrange the ions in order of decreasing radius by comparing their nuclear charges: O2- (smallest charge, largest radius) > F- > Na+ > Mg2+ (largest charge, smallest radius).