1. Lewis Structures, Covalent Bonding, and Electronegativity
Firas Cheema

2. Covalent Bonds Between two nonmetal elements
Electrons are shared rather than lost or gained
In covalently bonded molecular compounds, intermolecular forces are generally much weaker than the covalent bonds
Can be modeled with a Lewis structure

3. Covalent Bonds Using Lewis Model
Lewis structures shows molecular compounds as neighboring atoms sharing some or all of their valence electrons in order to attain octets(duet for H).
A shared pair of electrons is called a bonding pair
A pair that’s associated with only one atom is called a lone pair
Bonding pair of electrons represented by a dash
When two pairs shared it’s a double bond, three is a triple bond
Lewis model also shows why elements are diatomic
Ex. (Chlorine, Nitrogen, etc.)

4. Practice Problem
Write the Lewis structure for:
SCl2
CH4

5. Polar Covalent Bonds
Where electrons are unequally shared between elements
There is a positive and negative pole
The partial positive charge is written with a delta plus above it, the partial negative with a delta negative
Is the intermediate between a pure covalent bond a pure ionic bond
Most covalent bonds between dissimilar atoms are actually polar covalent

6. Electronegativity
The ability of an atom to attract electrons to itself in a chemical bond
Trends:
Generally increases across a period
Generally decreases down a group
Electronegativity is inversely related to atomic radius because the larger the atom, the less ability it has to attract electrons to itself in a chemical bond

7. Practice Problem Which element is more electronegative?
Carbon or Fluorine
Sodium or Potassium
Francium or Cesium