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The Atomic Volume, and Are Held There by the (VERY Dense) Nucleus

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The Atomic Volume, and Are Held There by the (VERY Dense) Nucleus - formed by subatomic particles: neutrons (neutral), protons (+), electrons (-) - electrons move through the atomic volume, and are held there by the (VERY dense) nucleus The Atom - the number of = 10-15 m subatomic particles determines the properties of atoms (and defines what is He called ªelementsº) = 10-10 m The atoms may be charged or neutral (how?) −27 −25 (how?) mass range: 1.67 × 10 to 4.52 × 10 kg size range: 62 pm (He) to 520 pm (Cs) Is it possible to have atoms of the same element with different mass?(Isotopes!) Is it possible to have atoms of the same element with different number of e-? (ions!) Each element has a unique Z Z = number of p+ What property do radioactive elements share? Can you find other elements usually known as pollutants? Why isotopes? Isotopes are great probes for: - past climate: water can be found as H216O, H217O and H218O but H216O (that is, the light isotope) evaporates preferentially. A signal of high H218O in the ocean (at a given time) indicates that a lot of water had evaporated, but not returned to the ocean! (how could this happen?) - human diet: where does our food come from? different plants have a different isotope content What other uses of isotopes do you know that can have an application in environmental sciences? Jahren and Kraft (2008) *mention UCSB project ªChildren of the cornº Can we get energy from atoms? ... fusion and fission ªThe sun is a mass of incandescent gas Your local (still active) A gigantic nuclear furnace G star Where hydrogen is built into helium At a temperature of millions of degrees SUN; Orion Arm, MW Yo ho, it©s hot, the sun is not ---X ray picture A place where we could live But here on Earth there©d be no life Without the light it gives (pictures not to scale) We need its light Your local (retired) We need its heat We need its energy nuclear plant Without the sun, without a doubt TROJAN; Rainier, OR There©d be no you and meº They Might Be Giants ---BW picture ± Why does the Sun shine http://www.johnharveyphoto.com/RoadTrip/NuclearReactor.html Oxygen commons.wikimedia.org www.brooklyn.cuny.edu/bc/ahp/SDPS/ It©s impossible to known for sure the position of an e-. e- will be more likely located in a place defined by the atomic orbitals (represented as clouds). Orbitals have names depending on: how close are they to the nucleus, their shape, and their orientation. FYI: its impossible to exactly solve the equations to describe the orbitals for atoms with more than 1 e-! (so we make approximations) 3d 1s 2p 3p http://csi.chemie.tu-darmstadt.de/ak/immel/script/redirect.cgi?filename=http://csi.chemie.tu-darmstadt.de/ak/immel/tutorials/orbitals/index.html Each orbital can be occupied by 2 electrons. Each orbital has a particular energy level. e- fill orbitals in such a way that they will occupy the next available orbital with the lowest energy level (Pauling exclusion principle). * quanta of energy Can you find this numbers in your periodic When forming molecules, atoms will table? tend to have electronic configurations such that their outer orbital is ªfullº, that is with 8 e- What would happen to e- that receives EM energy? It depends! (quantum states, spontaneous emission, electron binding energy, photoionization) Energy of EM waves: a wave consists of quanta of energy (photons). Energy of a photon depends on the frequency: E = hf = hc/λ What kind of EM radiation do you need to photoionize the h = 6.626 068 96(33) × 10−34 J s electron of an H atom given that its binding energy is 13.6 = 4.135 667 33(10) × 10−15 eV s eV? To what environmental 8 c = 3 10 m s-1 problems can this be related? UV radiation and DNA In spite of this ªsunscreenº effect, UV radiation can directly and indirectly damage DNA molecules. 1. Direct damage DNA and RNA bases subject to radiation return from the excited state to the lowest electronic ground state in a very short time. 2. Indirect damage, which occurs Bases have the ability to transform through the production of free radicals the energy in EM radiation into and reactive O species, is responsible vibrational energy and dissipate it for 92% of melanoma cases as heat. What is a free radical? Atoms interact with each other: chemical bonds Most elements occur in nature combined with the same element, or most common, with other elements. Exceptions: noble gases (He, etc.), some metals (Au, Cu, Ag, Pt). A chemical bond refers to the interaction that holds atoms together. This interaction occurs through the sharing or transfer of e- from one atom to another. Bonds make atoms function as a unit. There are different kinds of bonds, depending if the e- are shared or transferred and on how many e- are shared. Electronegativity: how attached am I to my electrons? Electronegativity of an atom will determine the kind of bond Which atoms are more likely to interact? http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Electronegativity.gif Types of chemical bonds Depending on the difference in electronegativity between the atoms, bonds can be: a) covalent: e- are shared b) polar: e- are shared but tend to be closer to the most electronegative atom Copyright 2000 Houghton Mifflin c) ionic: e- are transfered ... one example of ionic bond: table salt (NaCl)! Salt crystal Na loses its outer e- turning into a cation (positive ion). Cl receives the e- from Na turning into an anion (negative ion). http://www.semguy.com/gfx/nacl.jpg Na+ and Cl- have outer shell stable configurations. Na+ and Cl- are kept together by electrostatic interactions. Which represents Na+? which represents Cl-? why? http://www.computational-chemistry.co.uk/odyssey/screenshots.html ... examples of (single) covalent bonds: hydrocarbons! Methane CH4 Why is octane relevant for this class? Octane C?H? ... examples of (double) covalent bonds: more hydrocarbons! Ethylene ªEthylene is the most produced organic compound in the world; global production of ethylene exceeded 107 million metric tonnes per year in 2005.º (Wikipedia) Q. What can you do with ethylene? Is ethylene a renewable material? polyethylene foam and foam tape A. You can do polyethylene! www.airseacontainers.com polyethylene bottles What else from your http://www.deccofelt.com/materials.htm daily life is made of ªPolyethylene polyethylene tubing polyethylene? What polyethylene tanks There is no significant are the alternatives? Risk to your health She used to be beautiful once as well Plastic Bag Middle Class Polyethyleneº Radiohead ± polyethylene (B-side to OK www.buecomp.com/polyethylene.html computer) www.mmseptic.com/SepticTankInfo.html Bonding energy I Bonded atoms are more http://www.chem.ufl.edu/%7Eitl/2045/change/C9F11.GIF stable than separated atoms. Bonding energy II Beware! 1 double C=C bond = 614 kJ/mol 2 single C-C bonds = 696 kJ/mol Mole A mole is a chemical unit to denote the quantity of a substance. (Beware: the official definition is more subtle) If you have a mole of atoms, it means that you have 6.02 x 10 23 atoms. If you have a mole of molecules, it means that you have 6.02 x 10 23 molecules. ª1 mole of pennies distributed globally would Assuming 7 billion (7x109) people make us all trillionaires!º in the world, how many pennies correspond per person? Julie Wright, AS222d 2007 TA something useful: the molar mass (M) M = the mass of a mol of a substance Molar mass The molar mass of an element corresponds to the standard atomic weight of the element multiplied by the constant Mu = 1g/mol Where can you get the standard What is the molar mass of Carbon? atomic weight of the element? Atomic weight of Carbon = ? Why would you like to multiply M(C) = ? something by 1? The molar mass of a molecule corresponds to the sum of the standard atomic weight of the elements that make the molecule, multiplied by the constant Mu = 1g/mol What is the molar mass of Methane? What is the bonding energy found in the 107 metric million tons of ethylene (C H ) produced in 2005? 2 4 a) what is the bonding energy of 1 mol of ethylene 1 double C-C bond = ? 4 single C-H bonds = ? total = ? b) how many moles of ethylene are they in 107 million tons of ethylene molar mass of ethylene = ? 1 metric ton = 1000 kg Compare your answer to the global use of energy from fossil fuels and renewable energies (3.8 x 1020 Joules per year in 1999 - Physics Today, April 2002). Energy of reaction To calculate the energy of a reaction: ● find the chemical formulas for the substances of interest ● write down the reaction ● be sure the equation is balanced ● assume you will break all the bonds on the ªreactantsº (use energy), and that you will form all the bonds of the ªproductsº (release energy) ● subtract the energy used (left side of the equation) to the energy released (right) Lets burn some methane.. CH + 2O CO + 2H O 4 2 2 2 Where is the burning of CH4 used as an alternative source of energy? http://ecology.com/ecology-today/2008/10/10/ http://www.kentchemistry.com/links/Kinetics/BondEnergy.htm Why negative values? How much methane do we need to supply the requirements of annual global use of energy? .
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