CH02_2_ - Overview Atoms & Molecules Organization of...

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Unformatted text preview: Overview Atoms & Molecules Organization of Life of Life Elements of Life Atoms & Subatomic Particles Particles Periodic Table Overview Atoms & Molecules Chemical Bonds Bonds Non-Polar Covalent Non Polar Covalent Ionic Hydrogen Bio 230, Summer 2010, Ch2, Page 1 Fig. 2-1: 2Hierarchy of Life (Animal) Fig. 1-1: Hierarchy of Life (Plant) 1Chloroplast Chlorophyll Epidermis Leaf Leaf X-section Bio 230, Summer 2010, Ch2, Page 2 Matter Has mass (weight) and takes up space up space Composed of 92 natural elements Q&A What is an element? A substance that cannot be substance that cannot be broken broken down into simpler substances in a chemical reaction. Q: What are some examples of elements? Bio 230, Summer 2010, Ch2, Page 3 Fig. 2-10: Periodic 2Chart of First 18 Elements Elements Table 2-1: The Most Abundant Elements in Life 2Atomic Weight % 96% 4% Bio 230, Summer 2010, Ch2, Page 4 Trace Elements Less than 0.001% Boron (B) (B) Chromium (Cr) Cobalt (Co) Copper (Cu) Fluorine (F) Iodine Iron (Fe) Manganese (Mn) (Mn) Molybdenum (Mb) Selenium (Se) Silicon (Si) (Si) Tin (Sn) Vanadium (V) Zinc (Z) Fig. 2-10: Periodic Table 2- FOURTH SHELL 96% Potassium 19K Calcium 20Ca 4% Bio 230, Summer 2010, Ch2, Page 5 Matter When elements combine through chemical bonds they through chemical bonds they form form chemical compounds Chemical compounds have fi fixed ratios of elements Examples: H2O, CO2, CH4, NH3 Atoms Each element corresponds to a type of atom One atom is the smallest amount of an element still retaining the element’s retaining the element’s properties properties Bio 230, Summer 2010, Ch2, Page 6 Atoms Atoms are composed of subsubatomic particles Neutrons (nucleus) Protons (nucleus) Electrons (shells) (shells) - ++ - Helium = He Atoms Helium = 4He 2 - Atomic Number: Atomic Weight: ++ ++ ++ Bio 230, Summer 2010, Ch2, Page 7 - Atomic Arithmetic Atomic Number Equals number of protons Equals number of protons Determines type of element Atomic Weight (Mass) Equals number of protons + Equals number of protons neutrons neutrons Number of neutrons determines isotope Atomic Arithmetic Examples: Hydrogen = 11H; (0 neutrons) Helium = 24He; (2 neutrons) (2 neutrons) Carbon = 612C; (6 neutrons) Bio 230, Summer 2010, Ch2, Page 8 Atomic Humor Two atoms bump into each other. other. One says “I think I lost an electron!” The other asks, “Are you sure?”, to which the first replies: first replies: “I'm positive.” Atomic Atomic Humor A neutron walks into a bar; he he asks the bartender, “How much for a beer?” The bartender looks at him, and says “For you says “For you, … No charge.” Bio 230, Summer 2010, Ch2, Page 9 Fig. 2-10: Periodic 2Chart of First 18 Elements Elements Lessons From The Periodic Table In an uncharged atom, the number of p’s = the number of e’s Each element has a unique number of p’s in its atomic num nucleus Bio 230, Summer 2010, Ch2, Page 10 Lessons From The Periodic Table With increasing numbers of p’s and e’s, the e’s fill shells: 1st shell - 2 e’s 2nd shell - 8 e’s 3rd shell - 8 e’s (10 more e’s in row 4) Lessons From The Periodic Table A row in the periodic table contains a series of elements for one shell of electrons Elements in a row have diff different chemical properties Bio 230, Summer 2010, Ch2, Page 11 Fig. 2-10: Periodic 2Chart of First 18 Elements Elements Lessons From The Periodic Table A column in the periodic table contains elements with the same number of outer shell electrons Elements in a column have El similar chemical properties Bio 230, Summer 2010, Ch2, Page 12 Fig. 2-10: Periodic 2Chart of First 18 Elements Elements Lessons From The Periodic Table The major elements of life need different numbers of e’s to fill their outer shells H: 1, O: 2, N: 3, C: 4 The number of e’s in the outer Th shell determines the types of compounds an atom can form Bio 230, Summer 2010, Ch2, Page 13 Isotopes Isotopes have same atomic number, but different atomic weights weights Isotopes differ in number of neutrons Isotopes of an element behave the same in chemical reactions Isotopes In nature, most elements are a mixture of isotopes Example: on Earth, carbon is mixture of 612C, 613C, and 614C Some isotopes are radioactive; Some isotopes are radioactive; i.e. i.e., they decay spontaneously 614C 714N + ß - (electron) Bio 230, Summer 2010, Ch2, Page 14 Hydrogen Isotopes - + 3 1H Tritium 1 1H 2 1H + - + - Deuterium Isotopes in Research Scintillation Counting Figs. 2-6 & 2-7 22PET Scan Autoradiography Bio 230, Summer 2010, Ch2, Page 15 Q&A What is a chemical compound? A chemical compound forms chemical compound forms when when two or more elements combine through chemical bonds. Q: What are some examples of chemical compounds? Fig. 2-2: Chemical Compound 2- Na Cl NaCl Bio 230, Summer 2010, Ch2, Page 16 Q&A What is the smallest amount of a chemical compound called? called? A molecule: Two or more atoms connected by chemical bonds Fig. 2-12a: Non-Polar Covalent Bonds 2NonSingle Bond H—H H H Shell Diagram Hydrogen Molecule Structural Formula H2 Molecular Formula Bio 230, Summer 2010, Ch2, Page 17 Fig. 2-12b: Non-Polar Covalent Bonds 2NonOxygen Molecule Molecule Shell Diagram Double Bond O O=O O Structural Formula Formula O2 Molecular Formula Fig. 2-12c: Polar Covalent Bonds 2Shell Diagram O Water H O—H H H H2O Structural Formula Molecular Formula Bio 230, Summer 2010, Ch2, Page 18 Fig. 2-17b: Other Models 2- Space-Filling Model Ball-and-Stick Model O H Water (H2O) Fig. 2-18: Synapse 2- Bio 230, Summer 2010, Ch2, Page 19 H Fig. 2-19: Opiates 2- Enkephalin Fig. 2-12d: Non-Polar Covalent Bonds 2NonShell Diagram Methane H H H C H H— C—H H H CH4 Structural Formula Molecular Formula Bio 230, Summer 2010, Ch2, Page 20 Fig. 2-17c: Other Models 2Space-filling Ball-and stick Fig. 2-13: Water is Polar 2- Bio 230, Summer 2010, Ch2, Page 21 The Four Most Electronegative Elements 12n, 11p+, 11e– 11p 11e 11 23Na 18n, 17p+, 17e– 17p 17e Fig. 2-14: Ionic Bond 2- 17 Bio 230, Summer 2010, Ch2, Page 22 35Cl 11 23Na 17 + - 12n, 11p+, 10e– 35Cl 18n, 17p+, 18e– Sodium Chloride (NaCl) Fig. 3-7: 3Dissolution of Ionic of Ionic Compound Compound into Water Bio 230, Summer 2010, Ch2, Page 23 - - + + + + + + + Fig. 2-16: 2Hydrogen Bond + - + + + Bio 230, Summer 2010, Ch2, Page 24 Chemical Bonds A single chemical bond (-) (results results from atoms sharing a pair of outer-shell electrons outer Sharing allows atoms to complete outer shell Chemical Bonds Types of chemical bonds: Covalent non-polar: equal nonsharing Covalent polar: one atom has electron more often than other th atom Bio 230, Summer 2010, Ch2, Page 25 Chemical Bonds Types of chemical bonds: Ionic: one atom completely gives up electron(s), another takes it/them completely Hydrogen: weak interaction en: between + on H and - on nearby electronegative atom (N or O) NonNon-Polar Covalent Bonds Elemental molecules: H2, O2, N2 Chemical compounds: CH4 C-H bonds in most organic molecules C-C bonds in most organic bonds in most organic molecules molecules H3-C-CH2OH (ethyl alcohol) Bio 230, Summer 2010, Ch2, Page 26 Ionic Bonds Some ions are composed of several atoms NH4+ (ammonium) (ammonium) NO3- (nitrate) SO42- (sulfate) PO43- (phosphate) In solution, ions can dissociate from each other Ionic Bonds In a crystal, anions and cations are attracted to each other are attracted to each other, forming an ionic bond In solids ionic bonds are strong In solution, ions can dissociate In solution, ions can dissociate from from each other, yet are still attracted to each other In solution ionic bonds are weak Bio 230, Summer 2010, Ch2, Page 27 Q&A Why do elements combine in a fi fixed ratio to form a chemical compound? compound? Q&A Elements combine in a fixed ratio because they use chemical rati th bonds, bonds, and chemical bonds share electrons to fill their valence shells Each element valence shells. Each element requires requires a fixed number of electrons to fill its valence shell. Bio 230, Summer 2010, Ch2, Page 28 ...
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This note was uploaded on 11/28/2011 for the course BIOL 230 taught by Professor J.breckler during the Spring '11 term at S.F. State.

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