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CHAPTER 2

CHAPTER 2. Life’s Chemical Basis. Atoms. Element- fundamental substance consisting of only one type of atom. C, N, H, O are the most commonly occurring elements in the human body.

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CHAPTER 2

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  1. CHAPTER 2 Life’s Chemical Basis

  2. Atoms Element- fundamental substance consisting of only one type of atom. C, N, H, O are the most commonly occurring elements in the human body. There are 110 different elements, but only 92 naturally occurring ones. Numbers 93-110 are very unstable and degrade quickly.

  3. Na Ni Cs Hg You try it - Name the elements • Sodium • Nickel • Cesium • mercury

  4. Vocabulary • Matter – anything that takes up space and has mass • Subatomic particles – electron, protons, neutrons

  5. Levels of Chemical Organization • Subatomic particles • Atom • Molecules

  6. What Are Atoms? • Smallest particles that retain properties of an element • Made up of subatomic particles: • Protons (+) • Electrons (-) • Neutrons (no charge) • Note: protons and neutrons themselves are now known to consist of still smaller particles called quarks.

  7. Structure of an Atom • Nucleus • Contains protons and neutrons • Protons- subatomic particle with a small positive charge (+) • Neutrons- subatomic particle with no charge (0)

  8. Structure of an Atom

  9. Structure of Atoms electron proton neutron Hydrogen Helium

  10. Structure of an Atom • Shells around the nucleus of an atom contain electrons. • Electron- subatomic particle with a small negative charge (-) • An atom usually contains equal numbers of protons and electrons. When it doesn’t it’s called an ion.

  11. How to Read the Periodic Table See Appendix IV in back of textbook for good periodic table. Atomic Number- number of protons in a nucleus of an atom. This defines which element the atom is. Always the smaller number.

  12. Atomic Number = Protons • Symbol No O 8 Ca 20 Na 11 Cl 17 K 19 Fe 26 N 7

  13. How to Read a Periodic Table Mass Number- total number of protons and neutrons in the atomic nucleus. The larger number. Mass Number =Number of protons + Number of neutrons http://www.dayah.com/periodic

  14. You Try It! Symbol Protons Neutrons Mass O 8 8 16 Ca 20 ? 40 Na ? 12 23 Cl 17 ? 35 K ? 20 39 Fe 26 30 ? N 7 ? 14

  15. Putting Radioisotopes to work • Isotope- atoms with different numbers of neutrons. Isotopes have different mass numbers Example: • Carbon 12 has 6 protons, 6 neutrons • Carbon 14 has 6 protons, 8 neutrons

  16. Vocabulary • Radioisotopes – an isotope that spontaneously emits energy in the form of subatomic particles and x-rays when its nucleus disintegrates • Radioactive decay – isotopes that the nucleus is disintegrating and transforming one element into another spontaneously. (three types) • Half life – the amount of time for ½ of the mass of an radioactive isotope to break down

  17. Example: • Two isotopes of carbon • Carbon 12 (12C)and Carbon 14 (14C) • Carbon 14 • Half life -Decay time is 5700 yrs • If you have 100 grams of Carbon 14 after 5700 yrs you have 50 grams carbon 14 and 50 grams Nitrogen 13

  18. Decay example- The nucleus captures an electron which basically turns a proton into a neutron. Here's a diagram of electron capture with beryllium-7

  19. Radioisotopes • Have an unstable nucleus that emits energy and particles • Radioactive decay transforms radioisotope into a different element • Decay occurs at a fixed rate (half-life) • Carbon-14 becomes N-14 at a specific rate

  20. A “tracer” is a molecule in which a radioisotope has been substituted for a more stable isotope and can then be “traced” by the energy it releases as it decays. Radioisotopes can be used in medicine, ecology, botany and many other scientific fields.

  21. Popcorn Chemistry • When will each kernel pop? • After it pops, can it even go back to being a kernel? • What is released during the popping?

  22. Like popcorn, there is no way to know which radioisotope will degrade first! • Also like popcorn, once radioisotopes change, they can never return to their previous state.

  23. When radioisotopes degrade, energy is released. • Machines that can “see” this energy can be used to follow the path of the radioisotopes as they travel through a system, each one releasing energy as they degrade.

  24. Radioactive tracers can be used in: • PET scans • Pharmaceutical research • Metabolic studies • X-rays

  25. Concentrations of radioactive tracer bound to monoamine oxidase B (MAO B). Red shows the highest concentration. Clearly, lower concentrations are seen in the smoker. MAO B helps regulate nerve function and blood pressure.

  26. When atoms combine with atoms • Atoms acquire, share, donate electrons. • Whether one atom will bond with others depends on the number and arrangement of its electrons. • The atoms of some elements do this quite easily and other do not. • When an atom has one or more vacancies in orbitals, it interacts with other atoms by donating, accepting, or sharing electrons (forming chemical bonds).

  27. Electrons • Electrons occupy orbital's, or defined volumes of space around an atom’s nucleus. • Successive orbital's correspond to levels of energy, which become higher with distance from the atomic nucleus. • One or at most two electrons can occupy an orbital. • The atoms with vacancies in orbitals at their highest level tend to interact and form bonds with one another.

  28. Vacancy vs. No vacancy

  29. Electron organization • First shell- Lowest energy Holds up to 2 electrons • Second shell holds up to 8 electrons

  30. A model atomic structure is a diagram with successively larger circles, or shells, that keep track of all electrons in the orbital at a given energy level. Max number of electrons in each shell Shell Number electrons 1 2 2 8 3 18 4 32

  31. electron proton neutron CHLORINE 17p+ , 17e- SODIUM 11p+ , 11e- CARBON 6p+ , 6e- OXYGEN 8p+ , 8e- NEON 10p+ , 10e- HYDROGEN 1p+ , 1e- HELIUM 2p+ , 2e-

  32. Electron Vacancies • Unfilled shells make atoms likely to react • Hydrogen, carbon, oxygen, and nitrogen all have vacancies in their outer shells NITROGEN 7p+ , 7e- CARBON 6p+ , 6e- HYDROGEN 1p+ , 1e-

  33. You do it - Draw the shell configuration for each of these: • Na • Chlorine • K • Neon • Ca • 2, 8, 1 • 2, 8, 7 • 2, 8, 18, 1 • 2, 8 • 2, 8, 18, 2

  34. A B C • What are these elements? • Hint: It’s protons equal it’s atomic number, and since it is an atom so do the number of electrons.

  35. What are these elements? A= oxygen B= aluminum C= Nitrogen

  36. Periodic Table • Each element in a family or group on the Periodic Table has common properties • Examples • Valence electrons • Ion formation

  37. Ions • Lose electrons • Valence electrons 1-4 • Na = 1 valence = +1 ion • Be = 2 valence = +2 ion • B = 3 valence = +3 ion • C = 4 valence = +4 ion • Gain electrons • Valence electrons 4-7 • C = 4 valence = -4 ion • N = 5 valence = -3 ion • O = 6 valence = -2 ion • F = 7 valence= -1 ion

  38. When an atom or molecule loses electrons, it becomes positively charged. • For example, when Na loses an electron it becomes Na+. • Positively charged ions are called cations.

  39. When an atom or molecule gains electrons, it becomes negatively charged. • For example when Cl gains an electron it becomes Cl-. • Negatively charged ions are called anions. • An atom or molecule can gain or lose more than one electron.

  40. Valence Electrons of 8A- Noble Gases or Inert Gases Element Valance electrons He 2 Ne 8 Ar 8 Kr 8 44

  41. New Terms Chemical bond – joining one atom to another by electrons joining Compound – are molecules that consist of two or more different elements in proportions combined by a chemical bond Molecule – two or more atoms of the same element or different elements joined by a chemical bond 45

  42. New Terms Formula- the proportional arrangement and short hand for a chemical Chemical reaction- reacting two or more compounds and or molecules with one another Reactants – the things that are mixed together in a chemical reaction Products – the things that are produced in a chemical reaction 46

  43. Electron Vacancies Unfilled shells make atoms likely to react Hydrogen, carbon, oxygen, and nitrogen all have vacancies in their outer shells 47

  44. Chemical Bonds, Molecules, & Compounds Bond is union between electron structures of atoms Atoms bond to form molecules Molecules may contain atoms of only one element - O2 Molecules of compounds contain more than one element - H2O 48

  45. Formulas & Chemical Bookkeeping Use symbols for elements when writing formulas *****(Need to remember!) Formula for glucose is C6H12O6 6 carbon 12 hydrogen 6 oxygen 49

  46. Chemical Bookkeeping Chemical equation shows reaction Reactants ---> Products Equation for photosynthesis: REACTANTS PRODUCTS sunlight energy 12H2O 6CO2 + 6O2 + C6H12O6 + 6H2O ---> CARBON DIOXIDE WATER OXYGEN WATER GLUCOSE 12 oxygens 12 hydrogens 6 oxygens 6 carbons 12 hydrogens 6 oxygens 24 hydrogens 12 oxygens 6 carbons 12 oxygens 50

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