1. First electron shell  can hold 2 electrons  Outer electron shell  can hold 8 electrons  Hydrogen  H  Atomic number = 1 Carbon  C  Atomic number = 6 Nitrogen  N  Atomic number = 7 Oxygen  O  Atomic number = 8 Electron Chemical Properties of Atoms –Electrons determine how an atom behaves when it encounters other atoms. © 2010 Pearson Education, Inc.

2. The Chemical Basis of Life Energy levels of electrons Electron configuration and chemical properties: *chemical behavior due to electrons

3. Covalent Bonds –A covalent bond forms when two atoms share one or more pairs of outer-shell electrons. –Atoms held together by covalent bonds form a molecule. Name  molecular formula  Hydrogen gas  H 2  Oxygen gas  O 2  Methane  CH 4  Electron configurationStructural formulaSpace-filling modelBall-and-stick model Single bond  a pair of shared electrons  Double bond  two pairs of shared electrons 

4. Ionic Bonds –When an atom loses or gains electrons, it becomes electrically charged. Charged atoms are called ions. Ionic bonds are formed between oppositely charged ions. Outer shell has 1 electron Outer shell has 7 electrons The outer electron is stripped from sodium and completes the chlorine atom’s outer shell Na Sodium atom Cl Chlorine atom Complete outer shells The attraction between the ions—an ionic bond—holds them together Na  Sodium ion Cl  Chlorine ion Sodium chloride (NaCl)

5. Hydrogen Bonds –Water is a compound in which the electrons in its covalent bonds are shared unequally. This causes water to be a polar molecule, one with opposite charges on opposite ends. HH O  slightly   slightly – 

6. Hydrogen bonding Weak bonds formed between hydrogen and another atom –Surface tension of water Important as intramolecular bonds, giving shape to proteins and other biomolecules

7. WATER AND LIFE –Life on Earth began in water and evolved there for 3 billion years. Modern life remains tied to water. Your cells are composed of 70%–95% water.

8. Properties of Water Microscopic tubes Cohesion due to hydrogen bonds between water molecules Evaporation from the leaves SEM Flow of water Cohesion Adhesion

9. –Heat and temperature –Water can absorb and store large amounts of heat while only changing a few degrees in temperature. –Water can moderate temperatures. Properties of Water

10. –Surface tension is the measure of how difficult it is to stretch or break the surface of a liquid. Properties of Water

11. *solution *solvent *solute *aqueous solution Water is the solvent of life

12. The Chemical Basis of Life Hydrophilic and hydrophobic substances *hydrophilic*hydrophobic The dissociation of water molecules H 2 O H + + OH - Acids and bases *acid *base

13. Basic solution Neutral solution Acidic solution Oven cleaner Household bleach Human blood Pure water Grapefruit juice, soft drink Lemon juice, gastric juice Household ammonia Milk of magnesia Seawater Tomato juice Urine pH scale 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Increasingly acidic  greater H  concentration  Increasingly basic  lower H  concentration  Neutral [ H + ]  [ OH – ] Acids, Bases and pH

14. Carbon and Organic Chemistry –Carbon is a versatile atom. –Carbon forms large, complex, and diverse molecules necessary for life’s functions. –Organic compounds are carbon-based molecules. Structural formula Ball-and-stick model Space-filling model

15. Variations in Carbon skeletons Carbon skeletons vary in length Carbon skeletons may be unbranched or branched Carbon skeletons may have double bonds, which can vary in location Carbon skeletons may be arranged in rings Carbon and Organic Chemistry

16. –Larger hydrocarbons form fuels for engines. –Hydrocarbons of fat molecules fuel our bodies. Hydrocarbons

17. *structural isomers *geometric isomers *enantiomers Example of enantiomers: Chemical Components of Cells