Chapter Two Notes
Chapter Two Notes BIO 120
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This 4 page Class Notes was uploaded by Haleigh Siple on Monday September 7, 2015. The Class Notes belongs to BIO 120 at Grand Valley State University taught by Rybczynski in Summer 2015. Since its upload, it has received 47 views. For similar materials see General Biology in Biological Sciences at Grand Valley State University.
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Date Created: 09/07/15
Bio 120 Sept 6 Chapter 2 Notes Chapter Two The Chemical Context of Life Section 11 Matter anything that has mass and takes up space Exists in many forms e g gases metals rocks Element substance that cannot be broken down into simpler parts via chemicals There are 92 known Compound a substance make up of two or more elements 9 has different characteristics than elements Essential Gases 2025 of all elements elements living things need to survive and reproduce Oxygen 0 Carbon C hydrogen H and nitrogen N make up 96 of all living things Trace elements living things need only a small amount of these elements for survival Section 12 Atom smallest unit of measurement An element is made up of only one kind of atom which Nucleus consists of protons and neutrons center of the atom Protons positively charged particle found in nucleus Electrons negatively charged particle that reside somewhere within the nucleus cloud Neutron no charge found in the nucleus Dalton unit of measurement for subatomic particles Bio 120 Sept 6 Chapter 2 Notes Atomic Number the number of protons in an atom s nucleus Mass Number the sum of protons and neutrons in an atom s nucleus Mass Number Atomic Number number of Neutrons in nucleus Electrons are so small they are not included in the atom s mass Atomic mass the total mass of an atom Protons and Neutrons weigh 1 dalton So 2311N has an atomic mass of about 23 daltons Isotopes atoms of the same element with different numbers of neutrons and therefore different atomic masses Radioactive Isotopes an isotope Where the nucleus falls apart suddenly giving off particles and energy When decay leads to a decrease in a number of protons it transforms the atoms of one element into another element HalfLife the time it takes for half of the isotope to decay Radiometric Dating process of measuring the number of halflives that a sample has experience in order to determine the sample s age Bio 120 Sept 6 Chapter 2 Notes Energy the ability to cause change Potential Energy energy of a mass due to its locationstructure For example a boulder on a hill Electrons of an atom have potential energy based on the distance from the nucleus Electron Shells areas of electrons with different distances from the nucleus each with its own energy level Levels closer to the nucleus have less potential energy Valence Electrons electrons in the outermost shell These determine the chemical behavior of the atomelementisotope Valence Shell the outermost electron shell holds the valence electrons Some elements are mirt or chemically unreactive Incomplete valence shells cause elements to become radioactive Orbital the 3D space around the nucleus where the electrons are found about 90 of the time Section 23 Atoms with incomplete valence shells react with others to complete their valence shells They either share or give uptake valence electrons These interactions that hold atoms together are called chemical bonds Covalent Bonds a type of chemical bond where atoms share a pair of valence electrons Molecule chemical combination of atoms via covalent bonds Molecular formula 9 H2 Lewis Dot Structure 9 H H Structural Formula 9 HH the line represents a single bond Single Bond bond formed by a shared pair of electrons Double Bond bond formed by sharing two pairs of electrons in structural formula 00 Valence bonding activity based on the number of valence electrons needed to complete an atoms valence shell Electronegativity attraction of an atom to electrons to complete its valence shell The more electronegative the more it pulls electrons to itself Nonpolar Covalent Bond covalent bond between two atoms of the same element with the same electronegativity Bio 120 Sept 6 Chapter 2 Notes Polar Covalent Bond when atoms of different elements with different electronegativities bond and the electrons are not equally shared Ions two differently charged atoms or molecules resulting from the stronger electronegativity stripping the other of all its electrons Cation a positively charged ion Anion a negatively charged ion Ionic Bond the bonding of two ions of opposing charge Ionic Compounds or Salts the compound product of an ionic bond Salts are often found in crystal form Weak bonds can cause two molecules to bond interact and then separate Two kinds of weak bonds are 1 Hydrogen Bond the attraction between hydrogen and an electronegative atom 2 Van der Waals interactions electron clusters in an atommolecule causes areas of positive negative charge causing closeby molecules and atoms to stick together A molecules shapesize are important to its function Shape is determined by an atoms orbitals areas in electron cloud where electrons are found 90 of the time Biological molecules often form weak bonds Section 24 Reactants ingredients in a chemical formula Products resulting product of chemical formula Photosynthesis 6C02 6H20 9 C5H1205 602 Chemical Equilibrium the point at which the products and reactants remain in ratio and the concentration remains stable
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