1. Biology I Chapter 2-1 Of Atoms and Molecules: Chemistry Basics

2. ] I. The first job of a biologist is to understand the chemistry of life.

3. What does chemistry have to do with biology? Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

4. What‘s the matter? Matter is anything that has mass and takes up space. It is everything!

5. A. Atom The smallest “piece” of an element that retains the characteristics of that element. Composed of 3 subatomic particles: Protons Neutrons Electrons

6. Characteristics of Subatomic Particles

7. ] B. Because of its charges, the atom is neutral!

8. ] II. Elements ] A. An element is a pure substance that consists of one type of atom.

9. ] B. Abbreviations for the elements are called symbols. ] C. There are 92 naturally occurring elements.

10. How many of these elements are essential to life? ] Only 25!!!! ] The most abundant elements in living things are: F C (carbon) F H (hydrogen) F O (oxygen) F N (nitrogen)

11. III. Atomic number # protons in nucleus of an atom (establishes identity of the atom) Since most atoms are electrically neutral, atomic number indicates # of electrons as well. IV. Atomic mass # protons plus # neutrons in nucleus of an atom

13. How can we determine the number of neutrons in an atom? # neutrons = atomic mass - atomic # Determine # neutrons in a carbon atom (atomic mass = 12; atomic # = 6). # neutrons = 12 - 6 = 6 Do all carbon atoms have the same number of protons? Do all carbon atoms have the same number of neutrons?

14. V. Isotopes Atoms having the same number of protons, but differing numbers of neutrons. If an isotope is unstable, it is termed radioactive Ex. Carbon isotopes carbon 12 ( 12 C)  6 neutrons carbon 13 ( 13 C)  7 neutrons carbon 14 ( 14 C)  8 neutrons

15. ] Some isotopes are radioactive. This means that their nucleus is unstable and breaks apart emitting energy (radiation).

16. ] Some important uses of radioactive isotopes are: a. Dating fossils b. Treating cancer c. Tracers d. Killing bacteria

17. VI. Ions: sometimes atoms gain or lose electrons. This gives them a positive or negative charge. This is written as Na + or Cl -

20. VII. Compounds: A compound is a substance formed by the chemical combination of two or more elements. These are represented by formulas 3H 2 O Coefficient Subscript

21. Examples: 4CO 2 4 molecules of carbon dioxide 2C 6 H 12 O 6 2 molecules of glucose 6O 2 6 molecules of oxygen

22. Examples: CO 2 carbon dioxide H 2 O water CH 4 methane C 6 H 12 O 6 glucose

23. Chemical Reactions The reactants of a reaction are written to the left of the arrow. The products of a reaction are written to the right of the arrow. Example: 6O 2 + C 6 H 12 O 6  6H 2 O + 6CO 2 + energy

24. VIII. Chemical Bonds Chemical bonds involve the electrons in the last energy level. We call these electrons valence electrons! Octet rule! The goal of chemical bonding is for all atoms involved to complete or eliminate their outer electron shells.

25. ] The Octet Rule!!! ] Atoms can only handle a certain number of electrons in each energy level!! ] 2 in the first one They really, ] 8 in the second really want ] 8 in the third EIGHT!!!!

26. A.) Ionic bonds - form when oppositely charged ions are attracted to each other. atoms with 1, 2 or 3 valence electrons give up electrons to atoms with 7, 6 or 5 valence electrons which forms ions form salts which break apart in water Ex. NaCl

31. B.) Covalent bonds - form when atoms share electron pairs. Molecules are formed Covalent bonds are stronger than ionic bonds! The same size dogs SHARE the bone Atoms are the same Size and share the electrons equally!

33. Nonpolar covalent bonds - electrons are shared equally between atoms. Ex. methane

34. Polar covalent bonds - electrons are not shared equally. They are drawn more strongly to 1 atom’s nucleus than the other. Ex. water

36. Unequal sharing of the bone! ] One dog is larger than the other and hogs the bone, but they are still sharing!!!! ] One atom is larger and hogs the electron making one end of the molecule more negative and one end more positive!!

38. C.) Hydrogen bonds – involve hydrogen and are the weakest type of bond* Ex. DNA H2OH2O