1. Atoms and their interactions
Chemical Basis of Life
Atoms and their interactions

2. Atoms…. Proton = + charge Electrons = - charge Neutrons = no charge
Element = pure substance; only 1 kind of atom; can’t be broken down
Compounds = 2 or more different atoms combined; outer levels are full ex NaCl
Molecule = 2 or more of the same atoms combined ex. O2

3. Con’t. Electrons are found in energy levels around the nucleus.
Level 1 = 2 e- Levels above 1 hold 8 e-
E- are rearranged so that outer levels are full when cmpds are formed.
On the Periodic Table, the # of e- in the outer shell can be determined by what column it is in.

4. IONS!! Losing e- gives the atom a (+) charge. Gaining e- makes it (-)
Ion = charged atom
If the outer shell is full  unreactive/ inert/ stable ex. Ne, He
If not full  reactive/ unstable
ex. H, C
Why are ions important in Anatomy????

5. 3 types of Bonding…
1. Ionic  e- completely transfer to another atom; strong attraction
2. Covalent  sharing of e-
a. nonpolar (even sharing) ex. H2, O2
b. polar (one side pulls on e- more) ex. H2O
3. Hydrogen  extremely weak; creates surface tension of H2O

6. Why it matters…
Atoms are less stable as you move down the columns. The most stable is on the top.
Isotope = same # of p & e but different #’s of neutrons
** Life is Carbon based-- b/c C has the most bonding sites (4) and is the most stable; “stable yet reactive”

7. pH Scale ( 0 – 14)
Acids and bases are commonly found in our bodies and help us with chem. reactions like digestion.
Acids = pH 0-6 , are sour & react slowly w/skin ex. lemon jc.
Bases = pH 8- 14, are bitter, feel slimy, & sting in your eyes ex. soap
Neutral = pH 7 ex. water
Each step on the scale is 10X stronger
Both acids and bases get WEAKER as you move toward the CENTER of the scale.
Pg. 39??? What are buffers and why are they so important to life??