[Aahmsil]

Exams are around the corner and I was flicking through the Chemistry AS revision guide when I came across this:

When electrons are shared, the situation is more stable than when there are two separate atoms (four attractive forces between positive nuclei and negative electrons instead of two).

I'm afraid I didn't quite understand that statement. I may come off as thick but I'd rather be made to look foolish for a few minutes than live in foolish ignorance. So, can anybody clarify what these four/two attractive forces are? I'll be very grateful.

Thanks in advance!

[Coursework.info]

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[Jerry Zhou]

Suppose there are two atoms, A and B.
Firstly, if the two are bonded together.
the nature of a covalent bond is the attraction force between the shared electron pair and two nuclei, positive and negative, electrostatic force. The attraction force between A and bonded pair, attraction between B and attracted pair. So two forces.
However between non bonded two atoms, I don't quite understand either because I think this should be the case when van der Waals force comes in. I guess the statement in your revision guide could mean that, the attraction between the nucleus of A and the electrons of B, attraction between the nucleus of A and the electrons in A, and so forth. Therefore, there are four attractive forces, possibly. But personally, I think this will just perplex students a little bit, well, a large bit, as the case of two non bonded atoms resembles that inside noble gas. Eg, Two He atoms.
Hope that will help.

[Aahmsil]

Initially I too was in possession of the same reasoning but it seemed too simple. Now that you look at it though, it seems to be the only rational explanation. So, thank you for putting my mind at ease!