CHEMICAL BONDINGChapter 6.1

Objectives:1. Define chemical bond2. Explain why most atoms form

chemical bonds3. Describe ionic and covalent bonding4. Explain why most chemical bonding

is neither purely ionic nor purely covalent

5. Classify bonding type according to electronegativity differences

Chemical Bonding

In nature, most atoms are joined to others by chemical bonds

Types of Chemical Bonds

Ionic bonding – bonding resulting from electrical attraction between large numbers of cations and anions.

• Covalent bonding – bond resulting from the sharing of electron pairs between two atoms

Transfer of electrons

Why are most atoms chemically bonded to each other?

• As independent particles – high potential energy

• Nature – favors a minimized potential energy

• Most atoms are less stable by themselves than when they are combined

• By bonding, atoms decrease in potential energy, become more stable

Ionic Bond Examples

Covalent Bond Examples

Ionic or Covalent?

• Rarely purely ionic or purely covalent• Usually somewhere in between, depending on how strongly each atom attracts electrons. (Electronegativity)

• Determine by calculating difference in electronegativity

For example: Cs – 0.7 F – 4.0

So, 4.0 – 0.7 = 3.3 Use scale to determine

Difference in Electronegativity

1. If the electronegativity difference (usually called DEN) is less than 0.3, then the bond is nonpolar covalent.2. If the DEN is between 0.3 and 1.6, the bond is considered polar covalent3. If the DEN is greater than 1.7, then the bond is ionic.

Chart of polarities

Polarity

• Nonpolar-covalent bond : bonding electrons are shared equally by the atoms

• balanced distribution of electric charge

• Polar-covalent bond : bonding electrons are shared unequally by the atoms

• unbalanced distribution of electric charge

Examples of Polar and Nonpolar Covalent Bonds

Nonpolar

Polar

C - H

O - H

H - H

O - O