# Effects of orbital overlap and electronegativity on polarity of binary halogen acids

I have discerned these factors affecting orbital overlap:

1. Symmetry

2. Type of orbital

3. Nodes along the internuclear axis

4. $n$ quantum number of the atomic orbitals - the number of shells of electrons

5. Size of the atoms

6. Geometry of molecule

7. Angle of overlap

With respect to the binary halogen acids, I still have the following questions:

I can understand how one might argue that the binary halogen acids become more polar as one goes down group 7, in that electron density isn't very well shared; overlap is poor because of the small 1s orbital of hydrogen and the increasingly larger hybridized orbitals of the halogens. But this is half of what constitutes ionic character.

I.e. what about the electron on hydrogen? As the halogens get bigger, electronegativity decreases. How can the electron from hydrogen be isolated toward the halogen as EN decreases?

• Is your question referring to HX or H+ X- (reactant or products)? – ron Jun 22 '14 at 15:47
• It's referring to reactants. – Dissenter Jun 22 '14 at 15:54
• Why do you think the electron from hydrogen is isolated toward the halogen as EN decreases? – ron Jun 22 '14 at 15:59
• I don't see how the hydrogen electron is isolated toward the halogen as EN decreases. – Dissenter Jun 22 '14 at 16:00
• OK, it's not isolated toward the halogen as EN decreases. What's your question? – ron Jun 22 '14 at 16:02