Bio 240 Week 1 Notes
Bio 240 Week 1 Notes Bio 240
U of L
Popular in Biology
Popular in Biology
This 3 page Class Notes was uploaded by tpnguy09 on Saturday March 19, 2016. The Class Notes belongs to Bio 240 at University of Louisville taught by Dr. Rabin in Winter 2016. Since its upload, it has received 13 views. For similar materials see Biology in Biology at University of Louisville.
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I had to miss class because of a doctors appointment and these notes were a LIFESAVER
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Date Created: 03/19/16
Chapter 2: Chemical context of life 1/7/16 Why Chemistry? ● Bombardier beetle defense against ants ● Redox reaction ● Multidisciplinary science Matter Sodium + chlorine → sodium chloride (solid + liquid → salt (solid compound)) ● Diverse form ● Elements (92 in nature), compounds ● 6 Essential elements (CHONPS) (carbon, hydrogen, oxygen, nitrogen, prosperous, sulfur) ● Trace elements Atom ● Smallest unit with the properties of an element ● Nucleus ● Protons (+charges) ● Neutrons (no charge) ● Atomic number: protons, and determines what the element is, it doesn’t changes ● Mass number: protons + neutrons, can change, like isotopes Isotopes ● Same element with different # of neutrons ● Same atomic # ● Different mass # ● Can be used for o Carbon dating o Atomic bomb ▪ Iran and Uranium enrichment Energy levels of electrons ● First shell (2e-) ● Second shell (8 e-) ● Third shell (8e-) ● Moving outward from atomic nucleus: energy absorbed ● Moving inward from atomic nucleus : energy lost ● Electron configurations? ( SPDF) ● Chemical behavior of atom depends on o Valence shell o Valence electrons Periodic Table ● Atomic number, element symbol, atomic mass ● Ordered by shells Chemical bonds ● When atoms combine to form molecules and ionic compounds o Incomplete→ complete valance shells o Will only combine with another element that completes each other shells o Full 8e- ● Atoms share or transfer valence electrons o Hydrogen bonds? Covalent bond ● Two atoms sharing a pair of valence electrons ● 2H can share bonds to become H2 ● Pure element ● Compounds vs. molecule ● Single bond ● Double bond ● Note valence electrons ● Examples o Hydrogen H2 o Oxygen O2 (double bond) o Water H2O o Methane CH4 Electronegativity ● Attraction of a particular atom for the electrons of a covalent bond ● Nonpolar covalent bond (equal pulling) ● Polar covalent bond (unequal pulling) o Ex. Water ▪ 1H and 1 O are negative ▪ 1H is positive o Partial charges; negative and positive o Not pulling hard: positive o Pulling hard: negative ● Ionic bond o So unequal in valence shell attraction that electron stripped away o Bond is formed due to opposite charges ● NaCl→ Na+Cl- o Sodium atom + chlorine atom→ sodium chloride o Na=cation o Cl=anion ● Strong bonds, when you break them apart, they release more energy ● Weak chemical bonds o What’s the advantage? ▪ Easier to break, o Hydrogen bonds ▪ Weak bond individually, but when there are a lot of them they can become strong ▪ Ex. Water (H2O) and Ammonia (NH3) ● H positive, N negative
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