Class 2: Chemistry of Life

LOW electronegativity

Hydrogen

Carbon

HIGH electronegativity

Oxygen

Nitrogen

Ionic Bonds

bonds formed when negative and positive atoms are attracted to each other (exchange of atoms)

• BUT dissolves easily in water

Covalent Bonds

When 2 atoms share electrons

# of electrons that can be shared:

• 1 = H

• 2 = O

• 3 = N

• 4 = C

Single, double, triple bonds

• 1 = 2 shared e-

• 2 = 4 shared e-

• 3 = 6 shared e-

• # of e- pairs → # covalent bonds!!!

Non Polar Covalent Bond

equal sharing of e-

Polar Covalent Bond

unequal sharing of e-

• creates slightly positive and slightly negative areas around atoms

• higher e- density area → partial NEGATIVE (because e- are neg. → area becomes neg.)

weakest → strongest bonds

van Der Waals’ Forces → Hydrogen bonds → Ionic bonds → Covalent bonds 

Van der Waals

Electrostatic interactions → temporary partial charges

• weak, but a lot → STRONG

• geckos

Potential E and Strength = INVERSELY PROPORTIONAL

Higher potential energy in a chemical bond actually means the bond is weaker, while stronger, more stable bonds have lower potential energy. The potential energy of a bond is inversely proportional to its strength; breaking a weak, high-potential energy bond requires less energy than breaking a strong, low-potential energy bond.