2. Living things are highly ordered. There are approximately 25 elements that are essential to all living things. Four elements – carbon, hydrogen, oxygen and nitrogen make up about 96% of living matter. The other 4% include trace elements. Basic Chemistry for the Biologist

4. The World of Elements C Different kinds of atoms = elements H ON PSNa K Mg Ca

5. Elements 6 C Carbon 12.011 Atomic Number Symbol Name Atomic Mass

6. Atom The smallest portion of an element that retains its chemical properties

7. Element: A pure substance that cannot be broken down into other substances by chemical means. Atom: The smallest possible particle of an element. Nucleus: protons and neutrons tightly packed together in the center of the atom. Protons: Positive (+) electrical charge. Neutrons: No ( ) electrical charge. Shells: energy levels surrounding the nucleus in which electrons move around at a great speed. Electrons Negative (-) electrical charge.

8. Structure of the Atom

9. Atomic mass – add up the number of protons and neutrons

10. Ionic Bonds –Formed due to attraction between a cation and an anion –An ionic compound is a substance consisting of cations and anions bonded together –An example of ionic bond is the attraction between sodium ions and chloride ions

11. Isotopes: Atom with an altered number of neutrons

12. Molecules: Two or more elements bonded covalently Compounds : Two or more elements bonded ionically Chemical Reactions Reactants  Products

13. –carbon dioxide (CO 2 ) A compound is made of atoms of different elements bonded together. –water (H 2 O)

14. Bonds : Forces between elements that hold them together. Ionic Bond: A transfer of electrons from one element to the other. One becomes (+) the other (-). Na + Cl  NaCl Covalent Bond: Sharing of electrons in the outer most shell. H 2 + O 2  H 2 O Bonding song

15. Ions –Particle with one or more units of electrical charge –Results when an atom gains or loses electrons Cations—positively charged ions Anions—negatively charged ions

16. Ionic Bond Formed when atoms gain or lose (transfer) electrons Forms between a metal and a nonmetal Forms an ion with a charge –Positive ions and negative ions Sodium atom (Na)Chlorine atom (CI)Sodium ion (Na + )Chloride ion (CI - ) Na loses an electron to CI ionic bond gained electron

17. Ionic bonding

18. Covalent Bond Sharing of pairs of electrons Forms between 2 nonmetals Each atom has a filled valence shell covalent bonds Oxygen atom (O)Carbon atom (C)Oxygen atom (O) Carbon dioxide (CO 2 )

19. Covalent Bonds –Share electrons between atoms –Bond can be single, double, or triple

20. Covalent bonds

21. Carbon can form up to 4 covalent bonds! This lets it bond with lots of different elements, and make cool structures that all living things need.

22. Covalent bonds can be Polar or Nonpolar Polar Covalent Bonds – Electrons are not shared equally

23. Nonpolar Covalent Bonds Electrons shared equally No areas of partial charge

24. Water O HH _ ++

25. O HH _ ++ Life depends on hydrogen bonds in water. Water is a polar molecule. –Polar molecules have slightly charged regions. – Nonpolar molecules do not have charged regions. – Hydrogen bonds form between slightly positive hydrogen atoms and slightly negative atoms.

26. O HH _ ++ O HH _ ++ Hydrogen Bonds Attraction of a positive to a negative O HH _ ++

27. Hydrogen bonds –Tend to form between an atom with partial negative charge and a hydrogen atom covalently bonded to oxygen or nitrogen –Readily formed and broken –While individually weak, hydrogen bonds are strong when present in large numbers

28. Hydrogen bonding What does this mean for life? Ice is less dense than water Ice floats on top of water Lakes freeze from top down Animals/plants can live through the winter under the ice

29. Cohesion: Water molecules sticking together. Held together by weak hydrogen bonds. Adhesion: Water molecules sticking to other molecules by weak hydrogen bonds.

30. Capillary action: As water molecules stick to different surfaces, they pull other water molecules along with them

31. Hydrophobic: “water fearing” molecules repel water molecules because they are non-polar while water is polar. Examples: wax, oils, and fats

32. Hydrophilic: “water loving” Molecules are attracted to water molecules because both molecules are polar molecules. Solution: A uniform mixture of a solvent and a solute. Solvent: something that dissolves Solute: something that is dissolved

33. Amphipathic: Polar at one end non polar at the other. DetergentsPhospholipid Bilayer The Cell Membrane

34. Many compounds dissolve in water. A solution is formed when one substance dissolves in another. –A solution is a homogeneous mixture. –Solvents dissolve other substances. –Solutes dissolve in a solvent. solution

35. “Like dissolves like.” –Polar solvents dissolve polar solutes. –Nonpolar solvents dissolve nonpolar solutes. –Polar substances and nonpolar substances generally remain separate.

36. Some compounds form acids or bases. An acid releases a hydrogen ion when it dissolves in water. –high H + concentration –pH less than 7 more acidic stomach acid pH between 1 and 3

37. A base removes hydrogen ions from a solution. –low H + concentration –pH greater than 7 bile pH between 8 and 9 more basic

38. A neutral solution has a pH of 7. pure water pH 7

39. pH Scale: Describes how acidic or basic a solution is. Acid: Gives off excess H+ (Hydrogen Ions) when added to water. Example - HCl Base: Gives off excess OH- (Hydroxyl Ions) when added to water. Example - NaOH Buffer: Maintains pH in an acidic and alkaline environment. Natural buffers enable living organisms to maintain homeostasis.

40. Common Acids NameFormulaUses Acetic acidCH 3 COOH Vinegar Carbonic acidH 2 CO 3 Carbonated beverages Hydrochloric acid HClDigestive juices in stomach Nitric acidHNO 3 Fertilizer production Phosphoric acidH 3 PO 4 Fertilizer production Sulfuric acidH 2 SO 4 Car batteries

41. Acids Definition – Any substance that produces _______________ when mixed with water Properties: Taste sour Corrosive Conduct electricity Produce Hydrogen gas when exposed to metals

42. Common Bases NameFormulaUses Aluminum hydroxide Al(OH) 3 Deodorant, antacid Calcium hydroxide Ca(OH) 2 Concrete, plaster Magnesium hydroxide Mg(OH) 2 Antacid, laxative Sodium hydroxide NaOHDrain cleaner, soap products

43. Bases Definition – any substance that produces hydroxide ions (OH) or bonds with Hydrogen ions when mixed with water Properties Tasts bitter Feel slippery Dissolve oils and fats