1. Covalent Bonds Main Concept:
In covalent bonding, electrons are shared between the nuclei of two atoms to form a molecule or polyatomic ion. Electronegativity differences between the two atoms account for the distribution of the shared electrons and the polarity of the bond.

2. Covalent Bonding How Electronegativity Affects Bonding Generally
Covalently
Nonpolar
Polar
Bond Length and Bond Energy

3. - Electronegativity: ability of an atom in a molecule to attract shared electrons
- Electronegativity values generally increase left to right and decrease going down on periodic table
- trends can be understood qualitatively through the electronic structure of the atoms, the shell model, and Coulomb’s law

4. - Two or more valence electrons shared between atoms of identical electronegativity constitute a nonpolar covalent bond.
- However, bonds between carbon and hydrogen are often considered to be nonpolar even though carbon is slightly more electronegative than hydrogen 

5. - formation of nonpolar covalent bond can be represented graphically as a plot of potential energy vs distance for the interaction of two identical atoms
- Hydrogen atoms are often used as an example

6. - The relative strength of attractive and repulsive forces as a function of distance determine the shape of the graph
- bond length is
distance between
bonded atoms’ nuclei
= distance of
minimum potential
energy where
attractive and
repulsive forces are
balanced

7. - bond energy is energy required for dissociation of bond = net energy of stabilization of bond compared to two separated atoms; typically, bond energy is given on a per mole basis

8. Question:
How might larger or smaller distances between atoms influence bond energy and why?

9. - two or more valence electrons shared between atoms of unequal electronegativity constitute a polar covalent bond
- difference in electronegativity for two atoms involved in a polar covalent bond is not equal to zero

10. - atom with a higher electronegativity will develop a partial negative charge relative to the other atom in the bond
- For diatomic molecules, magnitude of partial negative charge on more electronegative atom = magnitude of partial positive charge on less electronegative atom

11. - Greater differences in electronegativity lead to greater partial charges, and consequently greater bond dipoles
- sum of partial charges in any molecule or ion must be equal to overall charge on the species

12. Question:
Order the following molecules in order from least to greatest bond dipole and explain why you ordered it that way.
Order the following molecules in order from least to greatest bond length and explain why you ordered it that way.
HBr
HCl HF

13. - All bonds have some ionic character, and difference between ionic and covalent bonding is a continuum
- differences in electronegativity are not the only factor in whether bond is ionic or covalent
- Generally, bonds between metal and nonmetals = ionic; between two nonmetals = covalent
- Examination of properties of a compound is best way to determine type of bonding