Chapter 2: Chemistry, Matter, and Life

1. Chapter 2:Chemistry, Matter, and Life

2. Overview

3. Key Terms

4. Chemistry • Science that deals with matter’s composition and properties • Used to understand normal and abnormal body function

5. Learning Outcomes Define a chemical element. Describe the structure of an atom. Elements

6. Elements Matter • The stuff from which the universe is made Elements • All of the different types of matter • Identified by names or chemicalsymbols • Also identified by number • Described and organized in theperiodic table 11 Sodium Na 22.99

7. Appendix 1 Periodic Table of the Elements What is the symbol and number for carbon?

8. Table 2-1 Some elements found in the human body.

9. Elements Atoms • Smallest subunits of elements • Cannot be broken down or changed by ordinary chemical and physical means

10. Elements Atomic Structure • Nucleus • At atom’s center • Composed of • Protons; positively charged • Neutrons; not charged • Electrons • Negatively charged • Orbit in energy levels around nucleus • Determine atom’s chemical reactivity

11. Figure 2-1 The oxygen atom. How does the proton number of this atom compare with the electron number?

12. Elements 8 Oxygen O 16.00 Atomic Number • Equal to the number of protons in an atom’s nucleus • Also represents the number of electrons orbiting the nucleus • No two elements share the same atomic number Oxygen’s nucleus contains 8 protons. Its atomic number is 8.

13. Elements Energy Levels • Regions around an atom’s nucleus where electrons orbit • Each region has space for a specific number of electrons. • The first energy level has room for 2 electrons. • The second energy level has room for 8 electrons. • An atom is most stable when its energy levels are filled with electrons.

14. Elements Energy Levels • Hydrogen has only one energy level with room for 1 more electron. • Carbon’s first energy level is full. • Carbon’s second energy level has room for 4 more electrons.

15. Elements Energy Levels • An atom will form chemical bonds with other atoms to fill its outermost energy level. An atom will donate, accept, or share electrons to fill its outermost energy level.

16. Figure 2-2 Examples of atoms. How many electrons does oxygen need to complete its outermost energy level? How does magnesium achieve a stable outermost energy level?

17. ✓ Elements Checkpoints 2-1 What are atoms? 2-2 What are three types of particles found in atoms?

18. ? Elements Pop Quiz 2.1 Which element makes up the greatest percentage of body weight? • Nitrogen • Oxygen • Potassium • Sodium

19. ? Elements Pop Quiz Answer 2.1 Which element makes up the greatest percentage of body weight? • Nitrogen • Oxygen • Potassium • Sodium

20. Learning Outcomes Differentiate between ionic and covalent bonds. Define an electrolyte. Differentiate between molecules and compounds. Chemical Bonds

21. Chemical Bonds • An atom forms chemical bonds with other atoms to fill its outermost energy level with electrons. • Electrons may be transferred between atoms. • Electrons may be shared between atoms.

22. Chemical Bonds Valence • The number of bonds an atom needs to fill its outermost energy level. 6 Carbon C 12.01

23. Chemical Bonds Ionic bonds • Form when one atom transfers electrons to another atom • The atom that donates an electron becomes a positively charged cation. • The atom that accepts an electron becomes a negatively charged anion. • The ionic bond is the attraction between oppositely charged ions. Na+ Cl– Cl– Na+

24. Figure 2-3 Ionic bonding. How many electrons are in the outermost energy level of a sodium atom? Of a chlorine atom?

25. Chemical Bonds Electrolytes • Compounds that separate into ions in solution • Term also used to refer to the ions themselves

26. Chemical Bonds Ions in the body • Ions play important physiologic roles in body fluid. • Homeostasis maintains proper ion concentration.

27. Chemical Bonds Ions in the body • Ions conduct electric currents in body fluid. • Measurement of a tissue’s electrical activity is used to diagnose disease.

28. Chemical Bonds Covalent bonds • Form when two atoms share electrons • The most common chemical bond in the body • Types: • Nonpolar covalent bond • Electrons are shared equally. • Polar covalent bond • Electrons are shared unequally.

29. Figure 2-4 A nonpolar covalent bond. How many electrons are needed to complete the energy level of each hydrogen atom?

30. Figure 2-5 Formation of water. How many hydrogen atoms bond with an oxygen atom to form water?

31. Chemical Bonds Molecules • Chemicals composed of two or more atoms held together with covalent bonds • Examples: O2, H2O Compounds • Chemicals composed of two or more different atoms held together by ionic or covalent bonds • Examples: NaCl, H2O, CO2

32. ✓ Chemical Bonds Checkpoints 2-3 What are the two types of chemical bonds and how are they formed? 2-4 What happens when an electrolyte goes into solution? 2-5 What are molecules and what are compounds?

33. ? Chemical Bonds Pop Quiz 2.3 What bond forms between two atoms that share their electrons equally? • Hydrogen bond • Ionic bond • Nonpolar bond • Polar bond

34. ? Chemical Bonds Pop Quiz Answer 2.3 What bond forms between two atoms that share their electrons equally? • Hydrogen bond • Ionic bond • Nonpolar bond • Polar bond

35. Learning Outcomes Define mixture. List the three types of mixtures and give two examples of each. Explain why water is so important in metabolism. Mixtures

36. Mixtures Mixture • A blend of two or more chemicals, elements, or ions

37. Mixtures The importance of water • Most abundant compound in body • Critical in all physiologic processes • Deficiency (dehydration) threatens health • Universal solvent • Stable liquid at ordinary temperatures • Participates in body’s chemical reactions

38. ✓ Mixtures Checkpoints 2-6 What is the difference between solutions and suspensions? 2-7 What is the most abundant compound in the body?

39. ? Mixtures Pop Quiz 2.6 Which term describes a substance that dissolves another substance? • Mixture • Solute • Solution • Solvent

40. ? Mixtures Pop Quiz Answer 2.6 Which term describes a substance that dissolves another substance? • Mixture • Solute • Solution • Solvent

41. Learning Outcomes Compare acids, bases, and salts. Explain how the numbers on the pH scale relate to acidity and alkalinity. Explain why buffers are important in the body. Acids, Bases, and Salts

42. Acids, Bases, and Salts Acid • A substance that donates hydrogen ions Base • A substance that donates hydroxide ions and accepts hydrogen ions Salt • A substance formed by a reaction between an acid and a base HCl  H+ + Cl– NaOH  Na+ + OH– HCl + NaOH  NaCl + H2O

43. Acids, Bases, and Salts The pH scale • Measures the relative concentrations of hydrogen and hydroxide ions in a solution • Scale from 0 (most acidic) to 14 (most basic) • Each unit represents a 10-fold change • Normal body fluid pH range is between 7.35 and 7.45 • Acidosis: body fluid pH <7.35 • Alkalosis: body fluid pH >7.45

44. Figure 2-6 The pH scale. What happens to the amount of hydroxide ion (OH–) present in a solution when the amount of hydrogen ion (H+) increases?

45. Acids, Bases, and Salts Buffers • Chemicals that prevent sharp changes in H+ concentration • Are important in maintaining a relatively constant pH in body fluids

46. ✓ Acids, Bases, and Salts Checkpoints 2-8 What number is neutral on the pH scale? What kind of compound measures lower than this number? Higher? 2-9 What is a buffer?

47. ? Acids, Bases, and Salts Pop Quiz 2.8 Which substance always accepts hydrogen ions? • An acid • A base • A buffer • A salt

48. ? Acids, Bases, and Salts Pop Quiz Answer 2.8 Which substance always accepts hydrogen ions? • An acid • A base • A buffer • A salt

49. Learning Outcomes Define radioactivity, and cite several examples of how radioactive substances are used in medicine. Isotopes and Radioactivity

50. Isotopes and Radioactivity Isotopes • Forms of an element that have the same atomic number but different atomic weight • Different atomic weight because of a different number of neutrons • May be stable or unstable (radioactive)