Electronegativity & Electronegativity Difference Supplemental Notes (Page 2 of 4) in pdf

Electronegativity & Electronegativity Difference Supplemental Notes Page 2

Electronegativity & Electronegativity Difference Supplemental Notes

1. Circle the element that has the highest electronegativity in each of the following sets.

a. K

b. N

c. Ba

What happens if two atoms of equal electronegativity bond together?

Consider a bond between two atoms, A and B. Each atom may be forming other bonds

as well as the one shown - but these are irrelevant to the argument.

If the atoms are equally electronegative, both have the same tendency to attract the

bonding pair of electrons, and so it will be found on average half way between the two

atoms. To get a bond like this, A and B would usually have to be the same atom. You

will find this sort of bond in, for example, H

or Cl

molecules. (

Note: It's important to realize

that this is an average picture. The electrons are actually in a molecular orbital, and are moving around all

This sort of bond could be thought of as being a "pure"

the time within that orbital.)

covalent bond - where the electrons are shared evenly between the two atoms.

What happens if B is slightly more electronegative than A?

B will attract the electron pair rather more than A does.

What happens if B is a lot more electronegative than A?

In this case, the electron pair is dragged right over to B's end of the bond. To all intents

and purposes, A has lost control of its electron, and B has complete control over both

electrons. Ions have been formed.

A "spectrum" of bonds

The implication of all this is that there is no clear-cut division between covalent and ionic

bonds. In a pure covalent bond, the electrons are held on average exactly half way

between the atoms. In a polar bond, the electrons have been dragged slightly towards

one end.

How far does this dragging have to go before the bond counts as ionic? There is no real

answer to that. You normally think of sodium chloride as being a typically ionic solid, but

All rights Jim Clark

and Eden Francis

Electronegativity & Electronegativity Difference Supplemental Notes Page 2