2.3 Chemical Bonding and Electronegativity
Electronegativity - the ability of an individual atom, when bonded, to attract bonding electrons to itself.
-Linus Pauling: developed a scale of EN values. He used the difference in EN between two atoms to
determine whether an ionic compound or molecular compound would be produced. (Remember earlier
we learned that ionic = metal + non-metal while molecular = 2 non-metals???? Well, it's not that
simple!)
-To determine if a bond will be ionic or molecular we must calculate electronegativity difference or ∆EN
(∆ is read delta). This difference tells us how likely an electron will be transferred from one element to
another
-The greater the ∆EN, the more likely a bond is ionic and an electron is transferred
Ex. NaCl what is the ∆EN? what kind of bond will be produced?
NOTE: WHEN ∆EN IS ≥ 1.7, AND IONIC BOND IS MADE!
-if your ∆EN difference is 0, that means electrons are EQUALLY shared and the bond is referred to as
NON-POLAR COVALENT (this is a molecular compound)
Ex. H2
-If the ∆EN is 0.1-1.6, that means electrons are UNEQUALLY shared and the bond is referred to as POLAR
COVALENT (this is a molecular compound).
-in a polar bond, electrons spend more time with the element that has a higher EN, so it appears as
though there are positive and negative poles in the molecule (note, electrons are not being transferred!)
A positive pole is represented by ɗ + while a negative pole is represented by a ɗ Examples: Draw the lewis structure for the following comopunds and determine the type of bond that
will be produced
1. HCl
2. Cl2
HOMEWORK: P. 73 #4-8
3. MgCl2
4. NF3