BIOL 112 Winter 2013
Schoeck – Lecture 1
Small Molecules 1: Chemical Bonds
The Periodic Table
Focus on these elements: Hyrogen, Carbon, Nitrogen, Oxygen, Phosphorus, and Sulfur (Yellow)
o Nitrogen and Oxygen make up our entire weight.
There are a couple of ions that should be noted also. (Pinkish red)
Recognize the Atomic number, Chemical symbol, and Atomic mass shown in periodic table.
o The number of protons defines the element.
o Atomic mass ≠ (exactly) protons + neutrons because of isotopes
Same number of protons, different number of neutrons.
Identical chemical properties, but could be unstable and radioactive.
Used in medicine as tracers. HBM
To form a molecule with chemical bonds, only the valence electrons matter.
o Molecule: 2 or more atoms bonded by a chemical bond.
1. Covalent Bond
a. Sharing of electrons (2 or more)
i. In H molecules, a pair of electrons shares a common orbital and spends equal
amounts of time around each.
ii. The nuclei keeps constant distance from repelling (both have positive charge)
iii. Very strong
iv. 3-D models can be predicted each covalent bond has a predictable length
and angle. (Chemistry is suggested here)
v. Double bond occurs when atoms share two pairs of electrons.
vi. Triple bond when three pairs of electrons are shared.
b. Follow the octet rule Atoms can form bonds until their valence shell is filled.
i. Carbon can form 4 covalent bonds to obtain the octet configuration.
c. POLAR COVALENT BOND: Unequal sharing of Electrons [I don’t know why thi