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Similar to Chapter 02 The Chemical Context of Life
Chapter 02 The Chemical Context of Life
- 1. The Chemical Context ofLife & Water and the Fitness of the Environment Chapters 2 & 3
- 2. Chapter 2-3 Chemistry /Water Learning Objectives • Identify subatomic particles and their properties • Use the periodic table to draw Bohr electron configurations • Utilize Bohr electron configurations to draw and describe ionic and covalent bonds • Identify and describe polar compounds and polar interactions such as hydrogen bonds • Convert pH values to hydrogen and hydroxide ion concentraton values • Describe and explain buffer interactions such as carbonic acid 2
- 3. Chapter 2-3 Chemistry /Water 3 Outline Chemical Elements Atoms Isotopes Molecules and Compounds Chemical Bonding Ionic and Covalent Hydrogen Properties of Water Acids and Bases
- 4. Chapter 2-3 Chemistry /Water 4 Elements Important for Biology Why were these two not included in the previous list?
- 5. Chapter 2-3 Chemistry /Water 5 Composition of Earth’s Crust versus Organisms Organic vs Inorganic matter
- 6. Chapter 2-3 Chemistry /Water 6 Atomic Symbols Key H 1.008 1 +1 -1 Hydrogen Atomic Number Atomic Mass
- 7. Chapter 2-3 Chemistry /Water 7 Periodic Table 12
- 8. Chapter 2-3 Chemistry /Water 8 Periodic Table Elements grouped in periodic table based on characteristics Vertical columns = groups; chemically similar Horizontal rows = periods; larger larger 1 H 1.008 3 Li 6.941 11 Na 22.99 19 K 39.10 4 Be 9.012 12 Mg 24.31 20 Ca 40.08 5 B 10.81 13 Al 26.98 21 Ga 69.72 6 C 12.01 14 Si 28.09 22 Ge 72.59 7 N 14.01 15 P 30.97 23 As 74.92 8 O 16.00 16 S 32.07 24 Se 78.96 9 F 19.00 17 Cl 35.45 25 Br 79.90 10 Ne 20.18 18 Ar 39.95 26 Kr 83.60 2 He 4.003 I II III IV V VI VII VIII 1 2 3 4 Groups Periods
- 9. Chapter 2-3 Chemistry /Water 9 The Bohr Model of The Atom(CHNOPS) 1 2 3 1H 9F 15P 9F Figure 2.9 , page 36
- 10. Chapter 2-3 Chemistry /Water 10 Updated model – Energy levels! Quantum mechanics requires a more versatile model Showing probability domains in 3 dimensions Electrons have the ability to move between these Orbitals !! This movement is very important for the use and Transfer of energy in biological systems !! ex: Photosythesis and cellular Respiration.
- 11. Chapter 2-3 Chemistry /Water 11 Octet Rule of atomic bonding Atoms with fewer than 8 electrons in outermost shell (except Hydrogen and Helium) are chemically reactive! If 3 or less – Tendency to donate electrons If 5 or more – Tendency to receive electrons This dictates what and how many atoms will form bonds!!!
- 12. Chapter 2-3 Chemistry /Water 12 Groups of Elements Semi-metals Elements on this side lose electrons to complete octet Elements on this side Gain electrons
- 13. Chapter 2-3 Chemistry /Water 13 Chemical Bonding Bonds are the result of either: A. Donating and Accepting electrons = Ionic bonds OR B. Sharing electrons = Covalent bonds
- 14. Chapter 2-3 Chemistry /Water 14 Formation of Sodium Chloride Ionically bonded sodium and chloride ions where the electron has been donated , forming the new compound sodium chloride
- 15. Chapter 2-3 Chemistry /Water 15Types of Bonds: B. Covalent Bonds Covalent bonds form between non-metals and other non-metals (elements on the right hand side of the periodic table) In this type of bonding electrons are shared and ions do not form.
- 16. Chapter 2-3 Chemistry /Water 16 Covalently Bonded Molecules Figure 2.12 page 38
- 17. Chapter 2-3 Chemistry /Water 17 The concept of polarity Polar means to have very different characteristics or to be opposites like the North and South poles of the earth. The concept of polarity is very important in biology. A molecule is said to be polar if it has two different characteristics at either end. The difference in characteristics is a difference in charge (+ or -) that results from an unequal distribution of electrons or an ionized subgroup.
- 18. Chapter 2-3 Chemistry /Water 18 Nonpolar Covalent Bonds Note: When non-metals bond (C, O, N, P, S) they tend to form non-polar bonds (of course we are talking about covalent bonds here because we are talking about non-metals) Electrons are shared equally between the bonded elements
- 19. Chapter 2-3 Chemistry /Water 19 Polar Covalent Bonds But, when non-metals bond with hydrogen they tend to form polar covalent bonds. (This is essentially because their charge density from protons (+) is much, much greater than hydrogen.) Electrons are not shared equally in polar covalent bonds.
- 20. Chapter 2-3 Chemistry /Water 20Types of Bonds: Hydrogen Bonds Water (H2O or H–O–H) is a polar molecule Electrons spend more time with O than H’s H’s become slightly +, O slightly – When polar molecules are dissolved in water The H’s of water molecules are attracted to the negative parts of the solute molecules Results in a weak bond – the hydrogen bond Easily broken, but many together can be quite strong
- 21. Chapter 2-3 Chemistry /Water 21 Water Molecule e-- e-- e-- e-- Fig. 2.13 p39
- 22. Chapter 2-3 Chemistry /Water 22 Hydrogen Bonding