Covalent Bonding

I.  Covalent Bonding Basics

   A.  Generally, covalent bonds form between nonmetallic elements.  Electron orbitals overlap so that the electron is shared between two atoms.

   B.  In a covalent bond, a pair of electrons is simultaneously attracted to two nuclei. 

    C.  The attraction of the electrons to two nuclei results in a lowering of energy, and a covalent bond is formed.

II.  Covalent Bonds and Lowered Energy 

***The bond length of a covalent bond is the distance of two nuclei at the minimum potential energy level.

C.  Lewis Dot Structures for Covalent Molecules

   1.  A Lewis dot structure is named for Gilbert Lewis, American chemist. 

   2.  Lewis dot diagrams help us to visualize bonds in a covalent molecule, as shown:

    3.  The rules for determining Lewis dot structures as easy to follow.  Review the following rules.

D.  Types of Covalent Bonds

   1.  Polar covalent bonds:  are bonds in which electrons are shared unequally.   THE MORE ELECTRONEGATIVE ATOM IN A POLAR BOND ALWAYS CARRIES THE PARTIAL NEGATIVE CHARGE.

• Sets of atoms with an electronegativity difference from 0.2 to 1.7 are considered POLAR COVALENT.

   2.  Nonpolar covalent bonds:  are bonds in which electrons are shared (fairly) equally.

• Sets of atoms with an electronegativity difference under 0.2are NONPOLAR COVALENT.

   3.  Coordinate Covalent Bonds: are bonds formed when one atom contributes both bonding electrons. 

   4. Resonance Structures:  are drawn when more than one Lewis dot structure for a molecules is possible.

E.  Analogies for Understanding the Different Types of Covalent Bonds