Understanding Non-Bonding Pairs of Electrons

[ace123]

[SOLVED] Ambiguous bonding question

Like I said it's just an ambiguous bonding question.

Non-bonding pairs of electrons

1. Create repulsions with other bonded atoms and other non-bonded pairs of electrons.

2. Do not influence molecular polarities because they are not involved in the formation of bonds.

3. Are responsible for resonance effects in molecules

4. Are counted as anti-bonding electrons when calculating bond orders of molecules.

5. Are localized on the least electronegative atom.

So I basically eliminated 3-5 as being wrong. But I'm unsure what they mean by non-bonding pairs of electrons. Are they referring solely to lone pairs or are they referring to core electrons. Which is why I'm stuck between 1 and 2. So I could use a little help. Thank you

 

[chemisttree]

Ignore the core electrons.

 

[ace123]

So that means that one is correct? Thank you for answering

 

[chemisttree]

And why not 2?

 

[ace123]

well because if they are lone pairs then they are positioned in a atom in such a way to minimize the repulsions between electrons. Is this not correct? Also I don't see how they could effect molecular polarities. I mean they don't effect polarity

 

[ace123]

So am I right? It doesn't really matter since the exam has passed but I would still like to know for the future.

 

[eli64]

lone pairs are responsible for polarity in many compounds (the majority in fact)

H2O has 2 lone pairs, and is the reason that water is polar - why ice is less dense than water etc...

 

[Kushal]

i can't get how the lone pairs are responsible for the polarity of water molecules(aain't you referring to h bonds??!). i always thought that it was because the oxygen is very electronegative; it should only depend on the effective nuclear charge, that is proton number and shielding effect.

lone pairs can build up shielding effect, and in this way affect polarity.

i'm still in high school, so i might be wrong...;)

 

[chemisttree]

lone pairs of electrons are areas of localized negative charge. That is practically the definition of polarity!

 

[Kushal]

oo right... guess my high school chem is a bit distorted...huh??!
thnks for pointing that out.

but what i said, does it make sense? that, e.g. in water, the oxygen atom attracts the bond pair in the O-H bond towards itself, and hence gets the negative charge. consequently, the hydrogen gets the positive charge. lone pairs have nothing to do except to bend the molecule??

thnks

 

[chemisttree]

No. The lone pairs are primarily responsible for hydrogen bonding. A huge effect.

 

[ace123]

Well the answer was one like I thought and I just realized that my previous post was incorrect. I meant that I don't see how it could not effect the polarities but the do not participate in bonding threw me off. Anyway I got it right and that is all that really matters. So thanks.