Login

The ionic character of the halides decreases down the group :
MF > MCl > MBr > MI, where M is a monovalent metal.
Kindly explain the reason for such an order.
[No links to this one plz, as I've already checked those answers, but, they are not satisfactory, so, explain in detail. :D]

Dear Student,

​As we move down the group, size of halogen atom i.e. anion increases. Greater the size of anion, greater is its tendency to get polarised i.e. higher is its polarisibility which is in accordance to Fajan's rule. Greater the polarisibility, greater is the polarisation and so greater is the covalent nature.
Therefore, covalent bond is preferred on moving down the group and hence tendency to form ionic bond decreases and hence, ionic character decreases.

  • 43
View Full Answer
Ionic character of any group is linked with its ability to lose or gain electron. In case of halides , these are monivalent groups which means requires only one electron to complete orbital. It decreases down as MF>MCl>MBr>MI. It is because of the fact as the size of the atom increases down the group i.e. block 17 , the pull of nucleus reduces at the outer end. The way fluorine is pulling an electron from a monivalent metal, the force is much stronger than iodine due to its smaller and compact size which facilitates the nucleus to expand its attraction zone. The zone reduces as the size increases and so ionic character decreases.
  • -1
Hello User , let us discuss your query

When we talk about the trend of atomic size in halides which is summarized as => when we go down in a group the atomic size is increasing because of the presence of more number of shells and the less attraction bettween nucleus and electrons .

When we talk about fluorine , chlorine , bromine and iodine

=> We found that fluorine is the smallest element so it have largest attraction bettween its electrons and nucleus while this attraction goes on decreasing in a gradual way for chlorine and bromine followed by iodine .

As fluorine is most electronegative among halides so it attract monovalent(having valency one or we can say have it needs one more electron to become stable ) atom .


As when monovalent comes near to fluorine it gets attracted by fluorine as because of net attraction force between fluorine nucleons and the electrons of monovalent atom .so monovalent atom M formed MF .

This attraction force between the fluorine and monovalent atom create a ionic property as ionic character is directly related with electronegativity which is nothing but tendency to attract electron from other atoms as fluorine is highly electronegative so it create more ionic character as compared to other halides .

Concept = more electronegative means more ionic character .

=> Similarily when we talk about cl atom ,then we can say it also have a good electronegativity so it also create a ionic character but less than fluorine .

=>Similarily due to large size as compared to F and cl , bromine too have less ionic character as because of large atomic size and less attraction bettwen its nucleus and the other monovalent atom's electrons .which decreases electronegativity difference so face less attraction .


=> And again in iodine , we have same situation as it is largest in size among halogens so it have very very less electronegativity (tendency to attract electrons ) so it is least ionic among halides .

So this is the whole concept behind ionic character trend of halides .

=> MF > MCl > MBr > MI

Hope you understand the concept !



=> You can refer to my posted image to see how fluorine have more attraction because of small size
As in my posted image i draw some hooks around the fluorine outer shell which represents that fluorine is always ready to attract any atom .and the hooks gradually fade away in other halogens because of less electronegativity or we can say due to large size.

  • 8
What are you looking for?