(a) K+ has more energy levels than Na+
(b) Both are in the same period Na+ radius is larger than Mg2+ because additional electrons in Mg2+ are added to same energy level and there is increase in number of protons in the nucleus leading to more force of attraction between the protons and electrons making Mg2+ smaller than Na+.
sharon kalunda answered the question on March 29, 2019 at 10:39
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