Comparing Polarizing Abilities of Molecules

[dibilo]

more covalent??

hi. i saw this problem while doing some chem revision. they wanted me to point out and explain which one of the two is "more covalent". these are my personal explanations.. but i am not sure if I am correct or am i using the right way to do it.. pls feel free to give me your guidance

LiF and NaF- Since Li is smaller in terms of atomic size, it has a higher polarizing ablility therefore it is more covalent. at the same time, since Na has a larger size, it is more suceptable to lose an electron therefore more ionic in nature

KCl and LiCl- <same explanation as above>

FeCl2 and FeCl3- FeIII due to its +ve charge/radius have a higher polarizing ability therefore FeCl3 is more covalent.

HgF2 an HgI2- My guess is HgI2 <<< didn't know how to explain

pls help :) thanks in advance

 

[chem_tr]

Atomic volumes are important in deciding whether the bond will relatively more covalent or not. In $\displaystyle LiF$, the atomic volumes are similar to each other; when the balance changes, they will be of more ionic nature, as in KCl. You can summarize this by cation/anion ratio.

In this viewpoint, $\displaystyle HgI_2$ is more covalent in nature, I think, your guess seems to be okay.

However, please note that I disagree with you about $\displaystyle FeCl_2$ and $\displaystyle FeCl_3$; but I may be wrong either.

 

[dibilo]

Atomic volumes are important in deciding whether the bond will relatively more covalent or not. In $\displaystyle LiF$, the atomic volumes are similar to each other; when the balance changes, they will be of more ionic nature, as in KCl. You can summarize this by cation/anion ratio.

In this viewpoint, $\displaystyle HgI_2$ is more covalent in nature, I think, your guess seems to be okay.

However, please note that I disagree with you about $\displaystyle FeCl_2$ and $\displaystyle FeCl_3$; but I may be wrong either.

thanks for the reply :)

anyone else have any views on this??

 

[Sirus]

As far as I remember, it is generally said that a bond is ionic if the electronegativity difference between the atoms is greater than 1.7. The greater the electronegativity difference between the atoms, the more ionic and the less covalent the bond. (correct me if I'm wrong)

 

[dibilo]

Atomic volumes are important in deciding whether the bond will relatively more covalent or not. In $\displaystyle LiF$, the atomic volumes are similar to each other; when the balance changes, they will be of more ionic nature, as in KCl. You can summarize this by cation/anion ratio.

In this viewpoint, $\displaystyle HgI_2$ is more covalent in nature, I think, your guess seems to be okay.

However, please note that I disagree with you about $\displaystyle FeCl_2$ and $\displaystyle FeCl_3$; but I may be wrong either.

"As the oxidation state of the metal becomes larger, the difference between the electronegativities of the metal and the nonmetal with which it combines decreases. The bonds in the compounds these elements form therefore become less ionic (or more covalent)." << found this on http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch8/valenceframe.html


FeIII have a higher oxidation state then FeII... therefore it should be more covalent right?