Re: Question Restated (was Re: Homework question

Marvin Margoshes wrote:

> "TC" <[EMAIL PROTECTED]> wrote 
>  
>
> > As I understand it, "covalent" refers to a specific 
> > subset of bonds that arise when the difference in 
> > electronegativity between the bonding atoms falls 
> > within a specific range.
The problem is that one cannot draw a sharp line in the sand
and say that this side of the line is covalent, and that ionic.  
You can pretty well describe extremes as covalent (tall
as in 2 meters) and ionic (short as in 1.3 meters) but
that is about it.  

> > Am I being a pedant?  Absolutely not. This is chemistry 
> > we're talking about here, not media studies or, god forbid, 
> > home economics.  It's as much about teaching our kids 
> > rigour, as about electrons.
> >    

That's wrong.  Actual science involves a fair amount of judgement,
and hard and fast rules are few and hard to come by.  While one
should simplify for beginners, providing clear cases as examples,
as practicioners one must also know the limits of such classification.
As MM points out, it is rare to find a HS chemistry teacher with
such expertise, and they are thus overfond of strict rules and often
react badly to being questioned.

> My hunch is that the problem is a teacher with poor knowledge of chemistry.
> It is hard to find good high school science teachers.  Too often, a teacher
> of some other subject is pressed into service.  How do I know this?  One way
> is postings in sci.chem in the past, from teachers in that situation who are
> desparate for help.
>
>  
josh halpern