2. AP Biology Basic Chemistry Review

3. Matter Anything that has mass and takes up space Composed of elements (atoms) Most common are CHNOPS

4. The Atom Nucleus: contains protons and neutrons Protons have + charge Neutrons have no charge # of protons = # of neutrons

5. The Atom # protons in nucleus determines the element Ratio of nucleus to atom size is like a pea is to the RCA Dome Electrons are in the energy levels

6. Electrons No mass Negative charge Attracted to the + charge of protons Atoms enter into bonds because of the attraction between + and -.

7. Bonds Ionic: electron transfer from one atom to another. The electron (-) is drawn away from one atom. This leaves the donating ion more +, and the ion that picks up the negative electron is now more negatively charged. NaCl: sodium had 11 electrons, chlorine had 17.

8. Covalent Bonds Shared electrons Each atom exerts an attraction to the other’s electron, but not enough to transfer it completely

9. Covalent Bonds Charge distribution may be equal Nonpolar: all atoms exert the same pull on electrons and share then equally. No charge at either end of the molecule O 2 Each oxygen molecule needs two electrons to complete it’s outer shell; enters into double bond with another.

10. Covalent Bonds Polar: atoms of different elements do not exert the same pull on electrons In H 2 O, O has more protons (8) and is more attractive to electrons than the two hydrogen atoms

11. More electrons spend their time near the oxygen atom. Therefore, it is more negative than the hydrogen ends of the molecule. Water is a polar molecule

12. Oxygen plays a huge role in biochemical pathways because of its high affinity for electrons. The polarity of the water molecule explains many of the properties of water.

13. Hydrogen Bonds A small electronegative bond of an atom in a molecule interacts with a hydrogen atom that is already in a polar covalent bond. May form between two or more molecules or within the same molecule.

14. http://www.biology.arizona.edu/ biochemistry /tutorials/chemistry/page3.html http://www.chemicool.com/