Chemistry Practice Problems Periodic Trends: Ionic Radius Practice Problems Solution: What is the correct order of decreasing size of th...

Solution: What is the correct order of decreasing size of the following ions? a. P3- > Cl- > K+ > Ca2+b. Ca2+ > K+ > Cl- > P3-c. K+ > Cl- > Ca2+ > P3- d. K+ > Cl- > P3- > Ca2+e. None of the above is correct.

Problem

What is the correct order of decreasing size of the following ions? 

a. P3- > Cl- > K+ > Ca2+

b. Ca2+ > K+ > Cl- > P3-

c. K+ > Cl- > Ca2+ > P3- 

d. K+ > Cl- > P3- > Ca2+

e. None of the above is correct.

Solution

We’re being asked to arrange the given isoelectronic series in order of decreasing ionic radius.


Recall that ionic radius is the size of an ion. The trend for the 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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