The Nature of Molecules Chapter Outline w figs

The Nature of Molecules Chapter Outline w figs - The Nature...

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The Nature of Molecules Chapter Outline 2.0 Introduction I. Enormous Explosion Marked the Beginning of the Universe A. Beginning of the Universe Began the Process of Evolution B. Evolution of Life and of Molecules Utilized Same Processes fig 2.1 2.1 Atoms are nature’s building materials I. Atoms A. Universe Composed of Matter 1. All matter made of atoms 2. difficult to study due to size 1
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B. The Structure of Atoms 1. Composed of smaller subatomic particles fig 2.2 a. Electrons (–charge) in circular orbits around nucleus 1), Same number as protons to balance charge 2) Dictates chemical activity b. Protons (+ charge) and neutrons (0 charge) in central nucleus 2. Atomic number = number of protons a. Neutrons and protons have same mass b. Only protons have electrical charge C. Atomic Mass 2
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1. Mass versus weight a. Mass is the amount of a substance b. Weight is the force of gravity exerted on it c. Atomic mass = mass of protons + mass of neutrons 2. Mass measured in daltons a. Proton or neutron is roughly 1 dalton b. Electron is 1/1840 dalton, practically mass-less D. Isotopes 1. All atoms of an element have the same atomic number (proton number) 2. An element cannot be broken into other substances by chemical means 3. Isotopes of an element have : a. Same number of protons, different number of neutrons b. Same number of electrons, thus same chemical properties 4. Example: Carbon-12 (12C) versus carbon-13 and carbon-14 fig 2.3 3
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5. Unstable forms, like carbon-14, decay a. Emit radioactive energy b. Half-life = time for half of a sample’s atoms to decay c. Potential harmful side effects, exposure must be limited E. Electrons 1. Electrically neutral atom has same number of electrons and protons 2. Electron orbit maintained by electrical attraction 3. In ions the number of electrons and protons are different a. Element that possesses a net electrical charge b. Positive charge if electron lost, a cation c. Negative charge if electron gained, an anion II. Electrons Determine the Chemical Behavior of Atoms A. Arrangement Determines Chemical Properties of Element 1. Orbital describes probable, not actual, location 2. Shapes differ. fig 2.4 a. Inner s orbitals are spherical b. More distant p orbitals are dumbbell-shaped c. Maximum number of two electrons per orbital 4
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3. Orbitals extremely far away from nucleus, atom mostly empty space 4. Nuclei of different atoms rarely contact one another 5. Electrons interact, determine chemical behavior B. Energy Within the Atom 1. Electrons (–) are attracted to protons (+) 2. Energy required to keep electrons in orbit
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This note was uploaded on 01/07/2010 for the course BIOL 2311 taught by Professor Burr during the Spring '08 term at University of Texas at Dallas, Richardson.

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The Nature of Molecules Chapter Outline w figs - The Nature...

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