My_Ch2_lecture(2009030423450422)

My_Ch2_lecture(2009030423450422) - Chapter 2: Chemical...

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Chapter 2: Chemical Bonding Purpose : review of basic chemical bonding, in order to better understand biochemistry (chemistry of living organisms) presented in Ch 3-5, and as a basis for understanding biological processes. What you MUST you know from Ch 2: Bonding (must know basic types) Electronegativity Hydrogen bonding (must know for H 2 O and DNA) Van der Waals Chemical Elements and Compounds matter —anything that takes up space and has mass 4 states of matter: on earth: solid, liquid, gas stars (includes the sun), gaseous planets: plasma element —substance that cannot be broken down to other substances by chemical reactions o 92 naturally occurring elements o 25 are needed for life (Table 2.1, pg. 24) O = 65% body weight (humans) C = 18.5% H = 9.5% N = 3.3% Ca, P, K, S, Na, Cl, Mg 1.5%-0.1% (each) Trace elements—needed in tiny amounts: B, Cr, Co, Cu, F, I, Fe, Mn, Mo, Se, Si, Sn, V, Zn compound —a substance that consists of 2 or more
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elements in a fixed ratio, with characteristics different than the component elements NaCl (table salt) contains Na (metal) and Cl (gas) in a 1:1 ratio; its chemical and physical properties differ from both Na and Cl Atoms and Molecules atom —smallest unit of matter that retains the properties of an element; made of subatomic particles: neutrons —in atomic nucleus, no charge (neutral), 1 Dalton (= 1.7 × 10 -24 grams) protons —in nucleus, positive charge, 1 Dalton electrons —outside the nucleus in orbitals, negative charge, 1/2000 of a Dalton (mass is ignored when computing atomic mass) atomic number = # of protons the atomic number is always the same for every atom of an element 2 He atomic number = 2 # of protons = 2 in an electrically neutral atom, # protons = # electrons = atomic # atomic mass = (# protons) + (# neutrons) (remember electrons have negligible mass) therefore, # neutrons = atomic mass – atomic # (#protons) 23 Na atomic mass = 23
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How many protons does Na have? 11 How many electrons does Na have? 11 How many neutrons? 12 **Note: Campbell’s suggests that the mass of an atom (mass #) = it’s atomic weight; however we will just use “atomic mass” isotopes —atoms that have a different # of neutrons than other atoms of the same element o isotopes with more neutrons weigh more
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This note was uploaded on 09/29/2011 for the course BIO 020.152 taught by Professor Pearlman during the Fall '08 term at Johns Hopkins.

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My_Ch2_lecture(2009030423450422) - Chapter 2: Chemical...

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