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Consider the isoelectronic ions Cl–, K+, and Ca2+. Which of the following is listed from left to rig

Consider the isoelectronic ions Cl–, K+, and Ca2+. Which of the following is listed from left to right in order of decreasing ionic radius? (largest radius first, smallest radius last) A. Cl–, K+, Ca2+

B. Cl–, Ca2+, K+

C. K+, Ca2+, Cl–

D. K+, Cl–, Ca2+

E. Ca2+, K+, Cl –


Solution: Isoelectronic ions have the same number of electrons. In order to compare the ionic radius, we must look at the number of protons. The more protons an ion has, the more they will pull on the electrons and make the radius smaller. Let's take a look at the Periodic Table for the number of protons which is equal to the atomic number. Cl has 17, K has 19 , Ca has 20. Therefore Cl- would have the biggest ionic radius and Ca2+ would have the smallest ionic radius.

Choice A is correct

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