Chemistry in Biology

Sept. 3, 2008

Top 11 elements in living things

• Oxygen (O), Carbon (C), Hydrogen (H)=93%

Nitrogen (N)=3.3%

Calcium (Ca)

Phosphorus (P)

Potassium (K)

Sulfur (S)

Sodium (Na)

Chlorine (Cl)

Magnesium (Mg)

Total =7.7%

Trace elements

Boron (B)

Chromium (Cr)

Cobalt (Co)

Copper (Cu)

Flourine (F)

Iodine (I)

Iron (Fe)

Manganese (Mn)

Molybdenum (Mo)

Selenium (Se)

Silicon (Si)

Tin (Sn)

Vanadium (V)

Zinc (Zn)

Basic vocab

• Element:– Smallest unit of material while

still maintaining properties.

• Atom: smallest unit of matter (protons, neutrons, electrons)

More vocab

• Compound:– Two or more elements combined

• Formed by bonding:– Covalent– Ionic– Hydrogen

Covalent bonding• Valence electrons are “shared”• Relatively stable bond• Double bonds (4 e- shared) and triple bonds (6 e-

shared) are even more stable than single bonds.

Polar covalent bonds

• In polar covalent bonds, there is unequal sharing of electrons (I.e. H20)

(-)

(+)

(+)

Nonpolar covalent bonds

• Charge (electrons) shared equally

Ionic Bonding• One atom “gives”

an electron to the other atom so both have complete outer shells

• Na+ ion & Cl- ion• Salts have ionic

bonds

Hydrogen Bonding

• Occurs between two polar covalent molecules (one has 1+ Hydrogen atom)

• Weak bonds, but crucial to living things