Session 2 (Review of Chemistry)

Session 2 (Review of Chemistry) - MCB 181 Study Session 2...

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MCB 181 Study Session 2 (Review of Chemistry)
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Learning Goals for Study Session 2 (Review of Chemistry) Be able to describe the components of atoms and define terms such as atomic number, atomic mass, isotope, and energy shells. Describe how atoms form covalent bonds and why covalent bonds between certain elements are polar. Be able to distinguish covalent bonds from ionic and hydrogen bonds, and hydrophobic molecules from hydrophilic molecules. Be able to briefly describe the chemical reasons for the special features of water molecules that make water uniquely suited to support life. Describe the process of ionization and define the terms anion, cation, acid, base, pH, and buffers. Describe how to calculate the molecular weight of a substance, how to make a solution of known concentration of that substance, and how to relate moles to numbers of molecules.
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We begin our discussion of molecules found in cells with a review of simple chemical principles governing how atoms are combined to form molecules. An atom is the smallest part of a chemical element that retains the properties of that element. Atoms consist of a nucleus of protons and neutrons surrounded by a cloud of negatively charged electrons . The number of protons or atomic number identifies the element. The number of protons and neutrons in the nucleus is approximately equal to the atomic mass of the element. Electrons have relatively little mass, but their number in the outermost orbit determines how atoms can be combined into molecules.
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Atoms are commonly depicted with protons (positive charge) and neutron (no charge) in the nucleus and the negatively charged electrons orbiting the nucleus in energy shells. There are strict rules governing the number of electrons in each energy shell. The number of electrons in the outermost shell relative to its maximum capacity determines chemical reactivity. As shown below, the hydrogen atom is unique because it consists of 1 proton and 1 electron, but no neutrons. Notice that carbon has only 4 electrons in an outermost shell that can hold a total of 8.
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Isotopes are atoms of the same element that have a different number of neutrons resulting in a different atomic mass. Isotopes of some elements are unstable resulting in decay at a
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This note was uploaded on 03/19/2011 for the course MCB 181R taught by Professor Leonard during the Spring '08 term at University of Arizona- Tucson.

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Session 2 (Review of Chemistry) - MCB 181 Study Session 2...

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