Ionic<.....>Covalent????

[quatumrulesoverall]

Hi all,

Would someone please give me the reason why molecule AlCl3 or BeCl2 are considered covalent bonding... ????

I have suggested to my tutor that because the EN difference is not so significant but she said it is not true???

Really long for the answer from all of you >>>>>???:cup: ;)

[ronthepon]

The larger the size of the anion with relation to the cation... the higher is the covalent charecter of the bond.

[quatumrulesoverall]

OMG!!! Yes, your rite, I have also thought of it. But it is not written in any textbook!!!! How come.? BTW can we talk more about it. Shall I have your IM nick?? :cup:

[ronthepon]

whassa IM nick? Can't we just discuss it here?

[quatumrulesoverall]

Thats a good idea, I just afraid that you wold go away.. okie, I ask you a quetion. Is it true that the size of the anion will outweigh the cation, and make it become covalent? and could you please explain a bit more why such thing happen? Is it because the big cation will have more chance to draw electron towards itself, if so sholud be ionic as NaCl???? I really confuse about it. plz give ma an answer!!

[ronthepon]

If the anion is small and the cation is bigger, then the total transfer of electrons gives them a condition of stablity.

 

All that can be understood by looking at how close the electrons eventually get to the nucleus. In large cations the electron is far away initially, thus is held loosely.

In small anions the electron gets an oppurtunity to get real close to the positive nucleus it seeks.

 

However, when it's a small cation, the electron is real close to the nucleus in the beginning. It is a stable state... the condition that the electron likes.

And with the anion, the electron can end up at a place quite far from the nucleus... so the electron will not be 'interested' in going to the anion.

 

In such a case, a covalent bond is a better option to form.

 

I hope you've got it.

[ronthepon]

And... just remember: cation: positive ion... anion: negative ion.

[quatumrulesoverall]

Thx very much, I really understand mcuh more about it ...

[Mercedes Benzene]

Also, if I may add, covalency vs. ionic(ness):hihi: can be determined through the Pauling Scale of Electronegativities. Now, keep in mind that the Pauling Scale is directly related to the size of the atoms, but I find it easier because it deals with a defined set of numbers.

Also, please feel free to see my last post in the "Chemistry 101" thread in the Chemistry forums.

 

 

(And sorry I couldn't figure out how to conjugate the word ionic in this post :hihi: :hihi:. I'm really tired right now.)

[ANUPAM.VERMA]

HI! LET ME GIVE U SOME GENERAL INFORMATION.WHEN THE DIFFERENCE IN THE ELECTRONEGATIVES OF THE TWO COMBINING ATOMS IS LESS THAN 1.7 COVALENT BOND IS FORMED.

IN CASE OF ALCL3,

E.N. OF AL=1.61 E.N. OF CL=3.16 DIFFERENCE=1.55. HENCE COVALENT.

 

IN CASE OF BeCL2,

E.N. OF AL=1.57 E.N. OF CL=3.16 DIFFERENCE=1.59. HENCE COVALENT.

 

IF THIS ANSWERS TO UR QUESTION DO SEND A REPLY..

PLEASE NOTE: THE FIGURES ABOVE ARE PAULING ELECTRONEGATIVITY VALUES. ALSO THIS IS THE SIMPLEST WAY TO ANSWER UR QUESTION.

[Jay-qu]

Please, in the future if you want your posts to not be deleted, dont post in all capitals B) thanks and welcome to Hypography.

[quatumrulesoverall]

Great appreciation for those who have helped me to tackle this question. Is there anyone who interested in finding other ways to explain this.. Please join us !!!!! B))