Covalent structures and bonding
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I cannot work out why in the graphs of electronegativity, the stable noble gases are at the troughs, but at the tops of peaks in graphs of ionisation energy! I would have thought in electronegativity the noble gases would also be at the peaks.
Igloo writes ...
You appear to understand already why the noble gases occupy the peaks of the plots of ionisation energy against atomic number. It is because the atoms of noble gases need the greatest amount of energy to remove an electron from their outer shells. In other words, in any particular period of elements, noble gases are the most difficult to convert into positive ions. This is the case because the 'effective nuclear charge' (taking into account inner shielding electrons) attracting teh electrons in the outer shell greatest at the right of each period.
Electronegativity, however, is measuring something quite different. It is a measure of an atom's pull of electrons towards itself in a covalent bond. However, amongst all the elements (and this includes metals), noble gases are the least inclined to form any type of covalent bond, so this is why their electronegativities are regarded as being extremely low indeed! On most scales their electronegativities are regarded as being irrelevant and aren’t quoted, and on others, as being zero or close to zero.
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updated: 26 November 2003
