Discussion Forum



1)

 The ionic radii (in Å ) of N3-,O2- and F- respectively are


A) 1.36,1.40 and 1.71

B) 1.36 , 1.71 and 1.40

C) 1.71 , 1.40 and 1.36

D) 1.71 ,1.36 and 1.40

Answer:

Option C

Explanation:

Number of elecrons in N3-   =7+3=10

 Number of electrons O2-= 8+2=10

Number of electrond F-  = 9+1=10

 Since all three species have every 10 electrons  hence they are isoelectronic species

  It is considered  that, in case  of isoelectronic species as the negative charge increases, ionic radii increases and therefore the value  of ionic radii are 

 N3-  =1.71  (highest among the three0

 O2-   =1.40

  F - = 1.36  9 lowest among the three)

Time Saving Technique.  There is no need to mug up the radius values for different  ions,  The particular question  can be solved  through following time saving.

Trick. The charges  on the ions indicate the size as  N3+   > O2-    > F -  . Thus , you have to look for the option in which the above trend is followed. Option (c) is only one in which this trend is followed. Hence, it is the correct answer.