Biology 1201 Chapter 2-Atoms
Biology 1201 Chapter 2-Atoms BIOL 1201
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This 5 page Class Notes was uploaded by Zachary Bergin on Wednesday September 7, 2016. The Class Notes belongs to BIOL 1201 at Louisiana State University taught by E. Wischusen in Fall 2016. Since its upload, it has received 7 views.
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Date Created: 09/07/16
Chapter 2 Atoms Monday, September 5, 2016 5:53 PM Atoms Smallest unit of matter separable by normal chemical means. Smallest unit of an element, that retains all of the elements properties. Organisms are composed largely of 11 basic elements. Subatomic Particles ParticleMass Electric Charge Proton 1 +1 Dalton Neutron 1 0 Dalton Electro 0 -1 n Dalton Atomic Structure Bohr Model Electrons moving in orbtials or shells around the nucleus. The electrons always try to be in the lowest orbital or energy shell (that is closest to the nucleus). The lowest level (K), can contain 2 electrons. The next level (L) can contain 8 electrons, and the next level (M) can also hold 8. Valence Atoms will try to gain or lose electrons in order to fill their outer shell or valence shell. The number of electrons to be gained or lost is called the Valence. # of Valen electrons ce Hydroge 1 1 n Helium 2 0 Carbon 6 4 Oxygen 8 2 Since isotopes have the same number of electrons they have the same valence and generally the same chemical properties. Bonds Characterized as strong or weak depending on the energy required to make/break the bond. Strong Covalent bonds involve sharing electrons. Weak -Non-covalent bonds Ionic interactions- attraction of opposite charges. One atom donates an electron to another. Hydrogen- bond between partially charged atoms. Bonds which are the result of very strong electrical attraction, where electrons are lost or gained are called Ionic Bonds. Form when Atoms gain or lose electrons. Strongest when dry. Bonds which are the result of electrical attractions, which are not so strong, where the electrons are shared are Covalent Bonds. The difference between Covalent Bonds and Polar-Covalent Bonds is that in Covalent Bonds share electrons evenly, and polar-Covalent Share Electrons unevenly. These bonds are strongest when in water. Difference between these bonds. Ionic Polar covalent Covalent Either gain Share electrons Share electrons or unevenly evenly lose electrons What Determines the number and type of bond's formed? Valence-Number Remember Valence is the number of electrons needed to fill the outermost shell of an atom. Valence electrons are the electrons contained in the outermost electron shell of an atom. Electronegativity-Type The measure of the tendency of an atom to attract a bonding pair of electrons. This measures the attraction an atom has for electrons. Hydrogen Bonds These bonds are the result of a hydrogen atom being bonded to another atom via a polar-covalent bond. Although these bonds are weak, in biological systems they are very important. Always involves Hydrogen Water molecules are a polar-covalent bond, but the attraction to other water molecules is a Hydrogen bond. Individual Hydrogen bonds are weak, but whenever there are a lot they are strong.' Molecules and Compounds Terminology: A compound is a substance that consist of 2 or more different atoms, in specific proportions, bonded together in a specific pattern. A molecule is the smallest part of a compound that retains all of he properties of the compound. Molecular Formulas Water H2O Carbon CO 2 Dioxide Glucose C8H 12 O 6 Isomers Molecules with the same molecular formula, but different arrangement of atoms. Ex.C14 Molecular Weight The sum of atomic masses of all the atoms in a molecule. Water H2O 18 Daltons Carbon CO2 44 Daltons Dioxide Sucrose C H O 342 12 22 11 Daltons insulin C254 37765 75 5,727 S6 Daltons Concentrations or Number of Molecules Gram Molecular Weight (Mole). The amount of a compound equal to its molecular weight in grams always contains the same amount of molecules (6.023 X 23 10 ). That is known as Avogadro's Number or 1 Mole. 1 Mole-the mass of a substance equal to its Gram Molecular Weight. In solution the concentration of a compound is measured by the number moles/liter of solution (molarity). 1 Molar Solution= a solution containing 1 Mole of a substance per 1 liter of solution. A solution containing 342 grams of Sucrose in a total volume of 1 liter is a 1 molar Solution.
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