1. Atoms, Molecules and Water Essential Building Blocks for Living Organisms

2. Comparison of Terms Atom Smallest units of matter that can exist separately. Element Chemical substance composed of the same kind of atoms Molecule Two or more atoms joined by chemical bonds

3. Composition of an Atom NucleusNucleus Proton = positively charged particle (+) Proton = positively charged particle (+) Neutron = uncharged particle (n or +) Neutron = uncharged particle (n or +) Number of protons + Number of neutrons = Atomic mass Number of protons = Atomic number C12 6 Electrons = negatively charged particlesElectrons = negatively charged particles Number of electrons = Number of protons Each electron circles the nucleus in an orbit representing a specific energy level.

4. Isotopes Forms of same atom that differ in the number of neutronsForms of same atom that differ in the number of neutrons Less stable isotopes generate radioactivityLess stable isotopes generate radioactivityC12 6 C13 6C14 6 radioactive

5. Atomic Models Hydrogen (H) Helium (He) Nucleus Electron Shell

6. Different Kinds of Atoms Helium Max 2e - Carbon +7p + +4p + +2p + Innermost electron shell +4e - +4n ± +2n ± +2e - Oxygen Max 8e - +7e - +8n ± Phosphorus +5p + +5e - +4n ± Calcium 2e- 2n 2p+ 6e- 6n 6p+ 8e- 8n 8p+ 15e- 16n 15p+ 20e- 20n 20p+

8. Applying Your Knowledge MagnesiumChlorine Atomic Number 1217 Atomic Mass 2435 Number of Protons Number of Neutrons Number of Electrons

9. Electron Energy Levels Energy Level Capacity for Electrons 12 28 38 In forming molecules, atoms combine to fill their outer energy levels.

10. Applying Your Knowledge MagnesiumChlorine Total Number of Electrons 1217 Number of Electrons in First Electron Shell Number Electrons in Second Electron Shell Number of Electrons In Third Electron Shell

11. Chemical Bonds Forces holding atoms together BondCharacteristics Ionic One atom loses an electron, another gains an electron Covalent Atoms share electrons Polar Covalent Atoms share electrons unequally Hydrogen Covalently-bound hydrogen is attracted to another atom

13. ± + – ± + ±+ ± +± + ± + ± + ± + – – –– – – ± + – – – ± + – ± + ±+ ± +± + ± + ± + ± + – – –– – – ± + – – – – – – – – – – Ionic Bonding in NaCl ± + – ± + ±+ ± +± + ± + ± + ± + – – –– – – ± + – – –– Sodium #e=2+8+1=#p ± + – ± + ±+ ± +± + ± + ± + ± + – – –– – – ± + – – – ––– – – – – Chlorine #e=2+8+7=#p – – Sodium ion #e=#p-1 Chlorine ion #e=#p+1 – Electron Completely Transferred Negative charge Positive charge

14. Ionic Bonding in NaCl Cl - Na + Opposites attract.Opposites attract. Sodiums nestle between chlorines.Sodiums nestle between chlorines. Perfectly cubical crystals form.Perfectly cubical crystals form. Cl - Na +

15. Covalent Bonding Oxygen Atom Oxygen Molecule (O 2 ) Oxygen Molecule (O 2 )

16. Polar Covalent Bonding Slightly negative Slightly positive

17. Hydrogen Bonds Join Water Molecules O O H H H H + + + – – + + Hydrogen Bonds Water molecules carry slight charges Positive and negative charges attract Hydrogen bonds form between H of one water molecule and O of another

18. Due to Hydrogen Bonding, Water Has Cohesion: water molecules associate with each otherCohesion: water molecules associate with each other Liquid at room temperatureLiquid at room temperature Fills blood vesselsFills blood vessels Flows freely to deliver materials throughout the bodyFlows freely to deliver materials throughout the body

19. Due to Hydrogen Bonding, Water Resists Temperature Change Water has high values for Specific Heat: heat needed to change temperature - keeps body temperature constant - keeps body temperature constant Heat of Vaporization: heat needed to convert liquid to gas - evaporation of sweat uses body heat  cooling - evaporation of sweat uses body heat  cooling

20. Due to Hydrogen Bonding, Density Decreases Upon Freezing Ice floats!

21. Water As a Solvent Substances that dissolve in water = hydrophilicSubstances that dissolve in water = hydrophilic –Polar –Ionic Substances that are insoluble in water = hydrophobicSubstances that are insoluble in water = hydrophobic –Non-polar

22. NaCl Dissolves in Water Ionic bonds of NaCl give +/- charges Water has partial +/- charges O tends to join with Na + H tends to join with Cl -

23. Dissociation + WaterWater– Hydroxide ion + Hydrogen ion A few water molecules naturally dissociate into ions Hydroxide ion is negative and basicHydroxide ion is negative and basic HydroxideHydroxide ion ion is negative and basic Hydrogen ion is positive and acidicHydrogen ion is positive and acidic HydrogenHydrogen ion ion is positive and acidic

24. The pH Scale Neutral [H + ] = [OH – ] Increasingly Acidic [H + ] > [OH – ] Increasingly Basic [H + ] < [OH – ] 0011223344556677889910101111121213131414 Lemon Juice Lime Juice Stomach Acid Beer Coffee Urine Water Blood Sea Water Baking Soda Bleach Ammonia Oven Cleaner Each 1-unit change in pH represents a tenfold difference in [H + ] and [OH - ]. [H + ] is highest at 0; [OH - ] is highest at 14. From 0  14, [H + ] decreases and [OH - ] increases. From 14  0, [H + ] increases and [OH - ] decreases.

25. Applying Your Knowledge Complete this sentence: Coffee has (A)______ fold greater (B) _____ than water. Given: Coffee has a pH value of 5. Pure water has a pH value of 7. (A) 1.1 2.10 3.100 4.1000 5.None is correct (B) 1.[H + ] 2.[OH - ] 3.[H + ] and [OH - ]

26. Maintaining Proper pH of Body Fluids Buffer: substance that resists pH change by combining with H + or OH -Buffer: substance that resists pH change by combining with H + or OH - –Example: bicarbonate buffering system of blood bicarbonate ion hydrogen ion carbonic acidcarbon dioxide water OH - +H 2 CO 3 HCO 3 - + H 2 O