Unit 2a: CHEMISTRY of LIFE An Introduction to Atoms and Molecules

1. Unit 2a: CHEMISTRY of LIFEAn Introduction to Atoms and Molecules

2. Introduction to Chemistry http://vimeo.com/83005599

3. Composition of Matter • 1. Matter - Everything in universe is composed of matter 2. Matter is anything that occupies space or has mass Mass – quantity of matter an object has • Weight – pull of gravity on an object

4. 3. Mass is a measure of the amount of matter in the substance a. Mass & weight are NOT the same b.   Weight is a measure of the pull of gravity on an object

5. 4. Matter exists in 4 states – solid, liquid, gas, & plasma

6. a. Solids have both a definite volume & definite shape (rock) b.   Liquids have a definite volume but no definite shape; they can be poured (water)

7. c. Gases do not have a definite volume or definite shape, but they take the  volume & shape of their container d. Plasmas have no definite volume, no definite shape, and only exist at extremely high temperatures such as the sun

8. 5. Chemical Changes in matter are essential to all life processes 6.   Biologists study chemistry because all living things are made of the same kinds of matter that make up nonliving things

9. B. Elements 1. Elements - Pure substances that cannot be broken down chemically into simpler kinds of matter 2. More than 100 elements (92 naturally occurring)

10. More than 100 elements have been identified, but only about 30 are important in living things 3. All of the Elements are arranged on a chart known as the Periodic Table

11. a. Periodic charts tell the atomic number, atomic mass, & chemicalsymbol for every element   http://www.youtube.com/watch?v=lMo6GkjVvEE

12. http://videos.howstuffworks.com/science-channel/27862-100-greatest-discoveries-the-periodic-table-video.htmhttp://videos.howstuffworks.com/science-channel/27862-100-greatest-discoveries-the-periodic-table-video.htm

13. 4.     Four elements, Carbon – C, Hydrogen – H, Oxygen – O, and Nitrogen – N make up almost 90% of the mass of living things 5. Every element has a different chemical symbol composed of one to two letters

14. 90% of the mass of an organism is composed of 4 elements (oxygen, carbon, hydrogen and nitrogen) • Each element unique chemical symbol • Consists of 1-2 letters • First letter is always capitalized

15. 6.    Chemical symbols usually come from the first letter or letters of an element like C for Carbon and Cl for Chlorine 7.   Some chemical symbols come form their Latin or Greek name such as Na for Sodium (natrium) or K for Potassium (Kalium)

17. C. Atoms 1. Atoms are the simplest particle of an element that retains all the properties of that element • Properties of atoms determine the structure and properties of the matter they compose • Our understanding of the structure of atoms based on scientific models, not observation

18. Atoms are too small to be seen so scientists have developed models that show their structure & properties • Atoms consist of 3 kinds of subatomic particles – protons & neutrons in the center or nucleus, and electrons spinning in energy levels around the center

19. 4. The nucleus is the center of an atom where most of the mass is concentrated

20. The Nucleus • Central core • Consists of positive charged protons and neutral neutrons • Positively charged • Contains most of the mass of the atom

21. Protons are positively charged ( p+ ), have a mass of 1 amu (atomic mass unit) , are found in the nucleus, and determine the atomic number of the element Example: Carbon has 6 protons so its atomic number is 6

22. The Protons • All atoms of a given element have the same number of protons • Number of protons called the atomic number • Number of protonsbalanced by an equal number of negatively charged electrons

23. 6. Neutrons are neutral or have no electrical charge (n), have a mass of 1 amu, are found in the nucleus, and when added to the number of protons, determine the atomic mass of the element • Example: Sodium has 11 protons and 12 neutrons so its atomic mass is 11+12=23 amu

24. The Neutrons • The number varies slightly among atoms of the same element • Different number of neutrons produces isotopes of the same element

25. Atomic Mass • Protons & neutrons are found in the nucleus of an atom • Protons and neutrons each have a mass of 1 amu (atomic mass unit) • The atomic mass of an atom is found by adding the number of protons & neutrons in an atom

26. 7. Electrons (e-) are negatively charged, high energy particles with little mass that spin around the nucleus in energy levels

27. The Electrons • Negatively charged high energy particles with little or no mass • Travel at very high speeds at various distances (energy levels) from the nucleus

28. Electrons in the same energy level are approximately the same distance from the nucleus • Outer energy levels have more energy than inner levels • Each level holds only a certain number of electrons

29. Energy Levels • Atoms have 7 energy levels • The levels are K (closest to the nucleus), L, M, N, O, P, Q (furthest from the nucleus) • The K level can only hold 2 electrons • Levels L – Q can hold 8 electrons (octet rule)

31. 10. Electrons in outer energy level are traveling faster & contain more energy than electrons in inner levels

33. 11. The number of protons (positive charges) and electrons (negative charges in an atom are equal so the net electrical charge on a atom is zero making it electrically neutral 12. Stable or non-reactive atoms have an outer energy level that is filled with electrons

35. http://www.pbs.org/wgbh/nova/physics/stability-elements.html • http://www.pbs.org/wgbh/nova/physics/hunting-elements.html

36. Periodic Table • Elements are arranged by their atomic number on the Periodic Table • The horizontal rows are called Periods & tell the number of energy levels • Vertical groups are called Families & tell the outermost number of electrons

38. http://www.pbs.org/wgbh/nova/physics/chemistry-elements.html

39. Compounds 1. Most elements do not exist by themselves • Readily combine with other elements in a predictable fashion

40. 2. A compound is a pure substance made up of atoms of two or more elements • The proportion of atoms are always fixed 3. Chemical formulas show the kind and proportion of atoms of each element that occurs in a particular compound

41. Molecules are the simplest part of a substance that retains all of the properties of the substance and exists in a free state • Some molecules are large and complex

42. Chemical Formulas • Subscript after a symbol tell the number of atoms of each element • H20 has 2 atoms of hydrogen & 1 atom of oxygen • Coefficients before a formula tell the number of molecules • 3O2represents 3 molecules of oxygen or (3x2) or 6 atoms of oxygen

43. 4. Compounds have different physical & chemical properties than the atoms that compose them (e.g. hydrogen & oxygen are gases but H2O is a liquid)

44. The physical and chemical properties of a compound differ from the physical and chemical properties of the individual elements that compose it

45. The tendency of elements to combine and form compounds depends on the number and arrangement of electrons in their outermost energy level • Atoms are most stable when their outer most energy level is filled

46. 5. The number & arrangement of electrons in an atom determines if it will combine to form compounds

47. Most atoms are not stable in their natural state • Tend to react (combine) with other atoms in order to become more stable (undergo chemical reactions) 6. In chemical reactions bonds are broken; atoms rearranged and new chemical bonds are formed that store energy

48. 7. Chemical bonds form between atoms during chemical reactions

49. Covalent Bonds 1. Formed when two atoms share one or more pairs of electrons

50. Covalent bonds (cont.) • 2.     Molecules form from covalent bonding & are the simplest part of a compound (e.g. H2O, O2)