Chemistry Study Guide 10/17/2016
Chemistry Study Guide 10/17/2016 Chem 121
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This 5 page Study Guide was uploaded by Pamela Crockett on Friday October 14, 2016. The Study Guide belongs to Chem 121 at University of North Dakota taught by David Pierce in Fall 2016. Since its upload, it has received 101 views.
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Date Created: 10/14/16
Filling Orbitals with Electrons Pauli principle: 2e-/orbital MAX Hund’s Rule – fill before pairing Ground State Configuration: [Ar] 4s2-3d1 Use PT (Periodic Table) to help write ground-state configurations The Periodic Table Grouped by behavior and property Order within shell (s-p-d-f) Fill lowest energy orbitals first! Atoms and Ionic Bonds Matter: Mixtures and Pure Substances Mixtures: Heterogeneous and Homogeneous Pure Substances: Elements and Chemical (83) Compounds (120 million) A compound is composed of two or more elements in definite proportions held together by chemical bonds…distinguished by its elements and bonds. Molecular Compounds Single neutral group (molecule) Held together by covalent bonds (shared electrons) Usually nonmetals H2: diatomic element…NOT a compound Ionic Compounds Not individual molecules Paired cations (+) and anions (-) Held together by ionic bonds Usually metal and nonmetal Organic Compounds All have C w/ H, O, N, and S Not just from living organisms Inorganic Compounds: All other elements Simple C compounds Molecules = combinations of atoms Compounds = combos of different elements Molecular compounds = greater than/equal to 2 non-metal atoms Ionic = cations + anions Chemical Formulas …How we write the “words” of chemistry… PCl3…CO2…ClO2…H2O2 DOES NOT EQUAL HO Molecular and structural formulas (center element with lines) Ball and stick model (elements as balls with attached sticks to other elements) Space filling model (bubbles) Formulas for ionic compounds… MUST be empirical MUST be neutral overall Mg2+ + Cl- = MgCl2 Al3+ +O2- = Al2O3 Ionic Bonds Ionic bonds form by complete transfer of one or more electrons from one atom to another A monatomic ion is only one atom with charge A polyatomic ion is a group of atoms with charge Naming compounds from formulas… Cation – monatomic (naming rule: element name – Roman “stock” number) Polyatomic (Ammonium: NH4+) Anions – monatomic Writing Lewis Structures: 1. Write skeletal structures 2. Count total # of valence electrons (# pairs) Electron-dot (Octet Rule) Structures: What is bonded to what in polyatomics? Central atom has lowest electronegativity and arrangement should be symmetrical Covalent Bonds and Molecular Structure VSEPR Model: easiest way to predict structurCharge clouds move to positions that Valence MAXIMIZE distances Shell: electron dot structures Electron Pair Repulsion: lone and bonding pairs repel each other VSEPR: 5 lowest repulsion geometry’s 1. Linear – 180 degrees 2. Trigonal planar – 120 degrees 3. Tetrahedral – 109.5 degrees 4. Trigonal bipyramidal – 90/120 degrees 5. Octahedral – 90/90 degrees Ionic Compounds: electrons transferred between atoms Molecular Compounds: electrons shared between atoms Main group atoms reach “octet” to bond!!! Telling the difference between Ionic + Covalent bonds…... Compounds show different behavior o Properties (formula mass, physical appearance, type of bond, melting point, boiling point) Gauge sharing with electronegativity o Difference: > or = to 2/Bond Type: Ionic > 0 and <2/Bond Type: Polar Covalent Naming Compounds from Formulas Binary Naming Rule: prefix + element name; prefix + element name + ide First element – no need for “mono” Examples: PCl3 = Phosphorous Trichloride N2O3 = Dinitrogen Trioxide
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