Chemistry Practice Problems Periodic Trends: Ionic Radius Practice Problems Solution: Which isoelectronic series is correctly arranged i...

Solution: Which isoelectronic series is correctly arranged in order of increasing radius?A) K+ < Ca2+ < Ar < Cl-B) Cl- < Ar < K+ < Ca2+C) Ca2+ < Ar < K+ < Cl- D) Ca2+ < K+ < Ar < Cl- E) Ca2+ < K+ < Cl- < Ar

Problem

Which isoelectronic series is correctly arranged in order of increasing radius?

A) K+ < Ca2+ < Ar < Cl-

B) Cl- < Ar < K+ < Ca2+

C) Ca2+ < Ar < K+ < Cl- 

D) Ca2+ < K+ < Ar < Cl- 

E) Ca2+ < K+ < Cl- < Ar

Solution

We’re being asked to arrange the given isoelectronic series in order of increasing radius


Recall that ionic radius is the size of an ion. The trend for ionic radius is as follows: it increases from right to left and down a period in the periodic table. Ionic radius also increases with an increasing number of electrons.


For this problem, we need to do the following:

Step 1: Determine the electrons in each species.

Step 2: Compare the charges if they are isoelectronic.


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