Electronegativity and Bonding Between Atoms

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Electronegativity describes how much an atom hold its electrons tightly. An atom that is less electronegative will be more likely to give up its electrons. The electronegativity of atoms determines the degree that electrons are transferred between molecules or shared between bonding atoms.

Mulliken presents a useful definition of electronegativity as the average of the ionization potential (IP) and the electron affinity (EA).

<math>\chi = \frac{IP + EA}{ 2}\,\!</math>

Note that the ionization potential is the energy required to remove an electron from an atom (to vacuum) and the electron affinity is the energy released when an atom captures an electron (into the lowest unfilled orbital).

The more electronegative the atom the lower the energy of the orbital within a given row.

Here is a summary of the different kinds of bonds.

Ionic Bonding	Polar Covalent Bonding	Covalent Bonding
Forms salts that dissociated in water	Forms bonds which have dipole	Forms bonds with no dipole
Between atoms of the far left and far right of the periodic table	Betwen atoms of different columns usually on the right side of the table	Between two like atoms
Large differences in electronegativities	Moderate differences in electronegativities	No difference in electronegativities
Very unequal sharing, electron is transferred form one atom to another	Unequal sharing of electrons	Equal sharing of electrons
Na+Cl-	C-F bond	F-F bond