Question

Licl has more covalent character than kcl but alf3 is more ionic than alcl3.why?

Answer 1

Answer:

Bonding is thought of more as a transition from pure covalent to pure ionic. Pure covalent is PH3 and pure ionic is CsF. Everything else is somewhere in the middle of this scale.

It's all to do with the differences in electronegativity. (pauling scale) Aluminium = 1.61 Chlorine = 3.16 Fluorine = 3.98 (most electronegative element there is)

So the difference tells you which atom has most of the electron density. Fluorine (being very electronegative) will "steal" a lot of electron density from aluminium making the bonds more ionic in nature than covalent.

Al- F difference = 2.37 Al-Cl difference = 1.55

Compare this to a well know ionic compound (NaCl = difference of 2.23) Based purely on electronegativity AlF3 is more ionic in character than NaCl.

But AlCl3 is covalent due to the low difference in electronegativity.

Answer 2

Answer:

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Explanation:

LiCl is more covalent than KCl because This is due to a phenomenon called polarization. It causes the formation of partial covalent character in an ionic bond. It depends upon four factors out of which two are : 1) Smaller the size of the cation, more the attraction and more the polarization. 2) Large the size of the anion, more the distortion and more the polarization. The anion here is same, Cl-, but the cation Li+ is much smaller than K+ and so more polarization occurs in LiCl, thereby making it more covalent than KCl.

But AlF3 is more ionic than AlCl3 because of the electronegativity difference between F- and Cl+ being more electronegative fluorine attract the more number of outermost electron of aluminium as compared to Cl which makes the compound more ionic