AP Biology Class notes from Dr. George's class turned into a study guide on Chemistry of life.
Everything is made up of matter
Only 25 elements are essential for life
Matter is made up of atoms
96% of living matter is N,H,C,O
Atoms consist of protons, Neutrons, and Electrons
4% of living matter is Ca,K,S,P
determine chemical behavior of atom
depends on the # of the electrons in the outermost shell called the "valance electrons" & "Valance shell"
atoms want a complete octate (8 valance electrons) except for hydrogen (wants 4)
Atoms tend to complete a partially filled valance shell or empty a partially filled valance shell.
This drives reactions & completes bonds
Bonds in chemistry
Covalent Bond -> share electrons evenly
Hydrogen Bond -> attraction between + and -
Why are covalent bonds so strong?
Multiple covalent bonds
* 2 atoms share a pair of electrons
* Double Bonds ex: O2
* both atoms are holding on
* 2 Pairs of electrons
* Very stable
* Triple bonds ex: N2 (very strong)
* Forms Molecules ex: H2O
* 3 pairs of electrons
Polar vs Non Polar Covalent Bonds
No areas of + or - because electrons are shared evenly
Electrons are shared unequally by atoms
Ex: Hydrocarbons (Methane CH4)
Ex: (H2O) -> O is more - and pulls electrons away from the H making O have a - charge.
Balanced and stable
Attraction between +H in one H2O molecule and the -O in another H2O molecule