Covalency and Oxidation Number in Covalent Compounds

1. Feb 14, 2013

hms.tech

1. The problem statement, all variables and given/known data

$NCl_{3}$

What is the Co-valency / Oxidation number of Nitrogen in this Covalent compound ?

2. Relevant equations

I think the table of electronegativity might be useful

3. The attempt at a solution

Nitrogen must be "-3" since it is more electronegative than Chlorine.

The correct answer is +3. How is that possible ?

Clearly Nitrogen is more electronegative than chlorine.

2. Feb 14, 2013

Saitama

Chlorine is more electronegative than nitrogen. :)

3. Feb 15, 2013

hms.tech

Nitrogen forms hydrogen bonds in its compounds with Hydrogen attached .

Chlorine rarely forms any hydrogen bonds in any of its compounds .

Here :

4. Feb 15, 2013

Saitama

Allen Scale?

Pauling Scale is the one you need to use.

5. Feb 15, 2013

hms.tech

hmm...doesn't Pauling scale gives us wrong values since according to pauling scale Chlorine being more Electronegative should form Hydrogen bonds .

6. Feb 15, 2013

Staff: Mentor

As if it all mattered...

First: oxidation numbers don't reflect any real property of the element, they are used just for electron accounting.

Second: using electronegativity to predict anything is a quite fuzzy concept, more of a general indication than a hard rule, especially when the differences in electronegativity are small.

Taking both things into account - don't be surprised you get inconsistent predictions trying to apply rule of thumb to border cases.