2.1 Basic Chemistry

1. 2.1 Basic Chemistry Matter is anything that takes up space and has mass. All matter, living or nonliving, is made up of elements.

2. 2.1 Basic Chemistry Elements are substances that cannot be broken down to simpler substances with different properties.

3. Elements that make up the Earth’s crust and its organisms.

4. Elements that make up 95% of living organisms (by weight) • C Carbon • H Hydrogen • N Nitrogen • O Oxygen • P Phosphorus • S Sulfur

5. Atom: The smallest part of an element that displays the properties of the element. • Atoms are made up of subatomic particles.

6. Subatomic Particles • Protons (positively charged) • Neutrons (uncharged) • Electrons (negatively charged)

7. Helium

8. Atomic Symbol Atomic Mass 12 C 6 Atomic Number Carbon

9. Atomic Symbol Atomic Mass = Number of Protons + Number of Neutrons Atomic Number = The Number of Protons in the Nucleus

10. The Periodic Table, See pg.A8 for more complete table

11. Isotopes 12 13 14 C C C* 6 6 6 *radioactive Atoms of the same element with a differing numbers of neutrons

12. Radiation • As radioactive isotopes decay, energy is released in the form of subatomic particles (radiation). • Alpha, Beta, Gamma rays – each with different energy (both dangerous and useful) • Cobalt 60 irradiation for sterilization of plastics, potasium 40, etc.

13. Some Uses of Low Levels of Radiation

14. Some Uses of High Levels of Radiation

15. Electrons • If an atom is electrically neutral, the number of protons (positively charged) is equal to the number of electrons (negatively charged).

16. Energy Levels (electron shells) • The first shell (closest to the nucleus) can contain two electrons

17. Energy Levels (electron shells) • The first shell (closest to the nucleus) can contain two electrons • Each additional shell can contain eight electrons

18. Energy Levels (electron shells) • The first shell (closest to the nucleus) can contain two electrons • Each additional shell can contain eight electrons • Each lower shell is filled with electrons before the next higher level contains any electrons.

20. Periodic Table (Revisited) Vertical columns indicatenumber of electronsin outermost shell VIII I 1 H 1.008 2 He 4.003 1 II VII III IV VI V Horizontal periods indicatetotal numberof electron shells 3 Li 6.941 4 Be 9.012 5 B 10.81 6 C 12.01 7 N 14.01 8 O 16.00 9 F 19.00 10 Ne 20.18 2 11 Na 22.99 12 Mg 24.31 13 Al 26.98 14 Si 28.09 15 P 30.97 16 S 32.07 17 Cl 35.45 18 Ar 39.95 3 19 K 39.10 20 Ca 40.08 21 Ga 69.72 22 Ge 72.59 23 As 74.92 24 Se 78.96 25 Br 79.90 26 Kr 83.60 4

21. Electrons • Atoms can give up, accept, or share electrons to have eight electrons in the outer shell. • Remember: Gain electron – gain negativity • Lose electron – lose balancing negative and thus Positive • Share electrons (pairs) – tightly binds atoms with no net charge

22. 2.2 Elements and Compounds • Molecules form when two or more atoms bond together (example: O2) • Definition: simplest unit of a compound • Other examples Carbon Dioxide ______ • Water ______ Methane _____ • Glucose __________

23. 2.2 Elements and Compounds • Molecules form when two or more atoms bond together (example: O2) • Compounds form when two or more different elements bond together (example: H2O)

24. 2.2 Elements and Compounds • Molecules form when two or more atoms bond together (example: O2) • Compounds form when two or more different elements bond together (H2O) • When a chemical reaction occurs, energy may be given off or absorbed.

25. Ionic Bonding • Ions are charged particles that form when electrons are transferred from one atom to another. Atoms that gain or lose electrons are called: Ions • Positive ions are Cations (positive charge, resulting from loss of electron) • Negative ions are Anions (negative charge, resulting from gain of electron)

26. Ionic Bonding • Ions are charged particles that form when electrons are transferred from one atom to another. • Ionic compounds are held together by an attraction between oppositely charged ions called an ionic bond.

27. Ionic Bonding

28. Covalent Bonding • In covalent bonds, atoms share electrons allowing each atom to have a completed outer shell. These are relatively “strong” representing stored Potential energy. • Please remember: covalent bonds are shared “pairs” of electrons; each atom is acquiring a more stable outer electron configuration

29. Covalent Bonding • A covalent bond • A double covalent bond

30. Shape of Molecules

31. Shape of Molecules • Shape is very important. Later you will see that shape in complex molecules like sugars, proteins, nucleic acids determines their particular function.

32. Nonpolar covalent bonds • If the sharing between two atoms is fairly equal, the covalent bond is described as nonpolar.

33. Polar Covalent Bonds If the sharing between two atoms is unequal, the covalent bond is described as polar.

34. Hydrogen Bonding • A hydrogen bond occurs between a slightly positive hydrogen atom of one molecule and a slightly negative atom of another molecule, or between atoms of the same molecule.

35. Hydrogen Bonding • Hydrogen bonds are very important in the final active shape-structure of key biomolecules like proteins • Hydrogen bonds in water give it very important unique qualities that make life possible on Earth.

36. 2.3 Chemistry of Water

37. Properties of Water • Water has a high heat capacity. • A calorie is the amount of heat energy needed to raise the temperature of 1g of water 1°C. • It only takes about 0.5 calories to raise the temperature of most other covalently bonded liquids 10C.

38. Properties of Water

39. Properties of Water • Water has a high heat of vaporization. A good coolant as it evaporates off of our skin.

40. Properties of Water • Water is a solvent. • The universal solvent; it dissolves more different kinds of subtstances than any other solvent. • Most of a cell is water.

41. Properties of Water • Water molecules are cohesive and adhesive. • Water molecules cling together because of hydrogen bonding (cohesion). • Water’s positive and negative poles allow it to adhere to polar surfaces (adhesion).

42. Properties of Water • Water molecules are cohesive and adhesive. • Water molecules cling together because of hydrogen bonding (cohesion). • Water’s positive and negative poles allow it to adhere to polar surfaces (adhesion). • So: Water is an excellent transport system, both outside and within living organisms.

43. Properties of Water • Water has a high surface tension • This allows some insects to walk on the surface of a pond or lake.

44. Properties of Water • Frozen water is less dense than liquid water. • Water that is frozen is going to “float”. • Fish in mountain lakes appreciate that.

45. Acids and Bases • Certain chemicals that are dissolved in water are called acids or bases. So a solution of water and these materials are called: • Acidic • Basic (alkaline) • Neutral

46. Acids and Bases • When water ionizes, it releases an equal number of hydrogen ions (H+) and hydroxide ions (OH-).

47. Acids and Bases • Acidic Solutions • Acids are substances that dissociate in water, releasing hydrogen ions (H+).

48. Acids and Bases • Acidic Solutions • Acids are substances that dissociate in water, releasing hydrogen ions (H+). • An example: HCl H+ + Cl- Every molecule dissociateswhen dissolved in water Hydrochloric acid is thus a strong acid.

49. Acids and Bases • Basic Solutions (Low H+ Concentrations) • Examples: Sodium Hydroxide, Ammonium Hydroxide

50. Acids and Bases • Basic Solutions • Bases are substances that dissociate in water, releasing hydroxide ions (OH-) or take up hydrogen ions (H+).