Electrons not shared with atoms. Electrostatic attractions keeps atoms together.
Electronegativity
Tells us how "Electron Hungry" a particular atom is.
Tells us the strength with which an atom attracts electrons.
Closer to filling octet = more electron hungry/ electronegative. Ie. Non metals.
Polarity
Farther From Filing Octet = low electronegativtiy. Ie. Metals
Covalent bonds generally mean sharing, but it's not fair and equally divided. When the sharing is not equal the molecule is polar.
The atoms that have higher electronegativty pull on the atoms that are shared more than others.
Delta Notation Electronegativity difference is determined to show whether a bond is covalent or ionic; as well as if a molecule is polar.
Three Types of Bonds
Delta Value Bond Type
0 Non- Polar Covalent
0.1-2.1 Polar Covalent
2.1+ Ionic
Example for calculating electronegativity difference: AEN F-Br 4.0-2.8=1.2 Bond is Polar-Covalent
Polarity-Delta Notation
Using delta notation you can display the direction of polarity.
Step 1: Determine Electronegativity values for each element.
Step 2: Subtract Electrnegativity values.
Step 3: Classify bond using electronegativity difference. If bond is polar covalent continue to step 4. If it is anything else, stop.
Step 4: Draw arrows pointing to where the electrons are being pulled.
In the bond shown (picture left) a lower case delta is placed over hydrogen to show that it is a little bit positive and a lower case delta is placed over fluorine to show it is a little bit negative. An arrow points to the direction that the electrons are being pulled toward (bigger electronegative number).
Interpartical Forces vs. Intrapartical Forces
Interpartical forces = very weak forces that result from polarity. Ex. Hydrogen bonding.
Inter= "Outside" a molecule.
Intrapartical Forces= bonds that hold molecules togther. Ex. Covalent Bond
Inra= "Inside" a molecule.
Hydrogen Bonding: a special type of interpartical attraction that happens between polar molecules with oxygen and hydrogen. Even though the attraction caused by polarities between the neighbouring particles is week, it takes a lot of energy to break these forces.
Non Metals= More Hungry
Full Octets = 0 electronegativity. Ie. Noble Gases
