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Lecture-2-Chemistry-_42283 - Liketheabiotic world,...

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The Chemical Nature of Life • 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, hydrogen oxygen & nitrogen % of hydrogen, oxygen & nitrogen comprise 96% of body weight 4%: Ca, K, S, Na, P, Mg, Cl atomic number element Human body wt. Trace elements (0.01%): I, Fe, Co, Zn, B, Mn, Se, Emergent properties : atoms molecules, example: 2H + O H O ; properties of 2 H 2 O elements O , H vs. that of water.
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ATOMS Atomic Structure 101 HAVE SUBATOMIC PARTICLES a. d. g. determine located in: combine to get located in 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 f electrons: (–) charge; atomic number Isotopes of an atom: different number of neutrons (proton & # electrons = # protons electron quantity identical) nucleus of: protons: (+) charge & neutrons (uncharged) – all exhibit same chemical properties R di i t t bl atomic mass Radioisotopes : unstable nuclei, decay giving off energy/matter. – can be detected; use as tracers to follow molecules in biological reactions Elements are neutral : # electrons = # protons Atomic number = # of protons in biological reactions. Also, many applications in medicine. # of protons 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. EX: Photosynthesis Electron transfers between molecules = transfers of energy these processes 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 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 3rd shell: 4 orbitals(8 e ’s max) **note that an atom has a 3 D Neon; atomic 2e 8e Is neon a a 3 D shape number 10 10e total 1 st shell 2nd shell reactive 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
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