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Lecture-2-Chemistry-_37185 - Liketheabiotic world,...

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The Chemical Nature of Life • Like the abiotic world living organisms are a collection of • Like the abiotic world, living organisms are a collection of atoms (representing different elements ) that are linked by chemical bonds to form molecules . • Unique to life, are the myriad of molecules primarily comprised of one or more of these four elements: carbon carbon, hydrogen, oxygen & nitrogen comprise 96% of body weight atomic number element % of Human body wt 4%: Ca, K, S, Na, P, Mg, Cl Trace elements (0.01%): I, Fe, body wt. Co, Zn, B, Mn, Se, Emergent properties : atoms molecules, example: 2H + O 2 H 2 O ; properties of elements O , H vs. that of water.
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ATOMS Atomic Structure 101 HAVE SUBATOMIC PARTICLES a. d. g. determine l t d i combine to get located in b located in: h b. atomic number e. h. shells constant for each may differ in various outer shell called c. f. isotopes i.
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Atomic Structure The element helium atomic number Isotopes of an atom: different number of electrons: (–) charge; # electrons = # protons neutrons (proton & electron quantity id i l) nucleus of: protons: (+) charge & identical) – all exhibit same chemical properties protons: ( ) charge & neutrons (uncharged) Radioisotopes : unstable l i d i i ff atomic mass nuclei, decay giving off energy/matter. b d t t d Elements are neutral : – can be detected; use as tracers to follow molecules in biological reactions. # electrons = # protons Atomic number = # of protons Also, many applications in medicine. Atomic mass = # of protons + # of neutrons
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Electrons Have Potential Energy • Potential energy: energy due to the arrangement or position of matter – An electron’s potential energy is proportional to its’ distance from the nucleus; determined by which energy level or shell the electrons occupy Energy absorbed by an atom can result in electrons moving to higher levels (shells), or even out of the atom altogether. Electron transfers between EX: Photosynthesis molecules = transfers of energy; these processes fuel metabolism.
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Distribution of Electrons in an Atom Electrons are in constant motion around the nucleus; occupy regions called orbitals , and these occur in discrete layers around the nucleus, termed shells . – Orbitals can hold a maximum of 2 e – The quantity of energy levels, or shells, is determined by the quantity of electrons: 1st shell: 1 orbital only (2 e ’s max) 1s 2nd shell: 4 orbitals (8 e ’s max) 2s 2px 2py 2pz 4 orbitals (8 e s max) 2s, 2px, 2py, 2pz 3rd shell: 4 orbitals (8 e ’s max) **note that note that an atom has a 3 D Neon; atomic number 10 2e 8e Is neon a reactive shape 10e total 1 st shell 2nd shell molecule?
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An Atom’s Electron Arrangement Determines Its’ Chemical Activity • Atoms with unpaired electrons in its’ outermost energy shell are reactive Æ termed valence electrons Neon is unreactive (outer shell completely filled with 8e ) Carbon: atomic # of 6:
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