Chemistry Week 2 Notes
Chemistry Week 2 Notes CHEM 211-003
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This 6 page Class Notes was uploaded by Lucas Kinsey on Tuesday September 13, 2016. The Class Notes belongs to CHEM 211-003 at George Mason University taught by Pritha G. Roy in Summer 2016. Since its upload, it has received 62 views. For similar materials see General Chemistry 1 in Chemistry at George Mason University.
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Date Created: 09/13/16
Lucas Kinsey Chemistry 211 George Mason University Chemistry 211 Week 2 Notes Chapter 2 Element: the simplest form of matter Compound: Consisting of 2 or more elements chemically bonded Mixture: 2 or more substances not chemically bonded Law of Mass Conservation: - The total mass of a substance does not change during a chemical reaction - Mainly applies to chemical reactions - The number of substances is subject to change but the total amount never changes Law of Definite Composition: No matter what its source, a particular compound is composed of the same elements in the same parts (fractions) by mass Mass Fraction = MAssof Element x∈Compound A Massof Compound A Mass Percent = Mass Fraction x 100 Mass of Element = Mass of Compound x Mass Fraction Mass of Element in Sample = Mass of Compound in Sample x Mass Fraction Law of Multipl- PCarbon Oxide I (CO) is 57.1% Oxygen and 42% - If elements A and B react to form 2 compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers Dioxide II (C0_2)is 72.7% Oxygen and - Example:.3% Carbon - We are looking for the proportion of Oxygen in both substances, so first we look for the ratio between the two elements in each substance, and we make it a 100g sample so the percentages will be easier to convert to grams - Carbon Oxide I = O = 51.7g = a ratio of 1.33g C 42.9g Dalton’s Atomic Theory: 1. All matter consists of atoms, which can neither be created nor destroyed 2. An atom of one element cannot be converted into an atom of another 3. Atoms of one element are all alike in their properties, but different from any other atom of any other element 4. Compound result from chemical combinations of different elements in a certain ratio Atomic # = # of protons in nucleus Mass # = Total # of protons and neutrons All atoms have the same atomic #, but can very in mass Isotopes: atoms of a certain element that have different numbers of neutrons and therefore different mass numbers - Mass # - Atomic # = # of Neutrons Isotopic Composition: Specifies the proportional abundance of each isotope - Atomic Mass Unit (amu) = Dalton (Da) o All relative to carbon ( ❑2C ) which has 12 amu exactly Mass Spectrometry: a method for measuring the relative masses and abundances of atomic- scale particles precisely Isotopic Mass: the relative mass of an isotope - Isotopic mass of 2Si = Measured Mass Ratio x Mass of 12C = 2.33 ❑ ❑ x 12 amu = 27.97 amu Calculating Atomic Mass of an Isotope: - Atomic Mass = (Frequency of 1 Isotope (%) x Mass (amu) of 1 st nd nd Isotope) + (Frequency of 2 Isotope (%) x Mass (amu) of 2 Isotope) Concerning the Periodic Table: - Periods are the horizontal rows (#ed 1-7) - Groups are the verticle columns (1-18) - Majority of elements are metals, they are solid at room temperature and conduct heat and electricity - Nonmetals are not conductive - Metalloids are mixed properties between metals and nonmetals - Elements in the same group have similar chemical properties while same periods have the same layers of electrons 2 Types of Chemical Bonds: 1. Atoms sharing electrons are Covalent bonds and act as a single unit 2. Atoms transferring electrons is an Ionic Bond and are individual units in an array Ions: charged particles that form when an atom gains or loses one or more electrons Binary Ionic Compound: Composed of two elements (usually a metal and a nonmetal) - Metal loses and atom and becomes a positively charged cation - Nonmetal gains an electron and becomes a negatively charged anion **All binary ionic compounds are solid arrays of oppositely charged ions Monatomic ion: a cation or anion that is derived from one atom Coulomb’s law: - The energy of attraction (or repulsion) between two particles is directly proportional to the product of the charges and inversely proportional to the distance between them Charge1xCharge2 - Energy α distance Because ionic compounds are all neutral, we can predict the number of electrons los or gained - The goal is for each atom to end up with the same number of electrons as the nearest noble gas Typical Scenario: nonmetals gain, metals lose Rules for naming Binary Ionic Compounds: 1. In all ionic compounds, names and formulas give the positive cation first, and the negative anion second 2. For all binary ionic compounds, the name of the cation is the name of the metal and the anion has the suffic “-ide” added on to the end a. Example: Calcium Bromide Common Monatomic Ions: Charge Name Formula Cations 1+ Hydrogen H+ Lithium* Li+ Sodium* Na+ Potassium* K+ Cesium Cs+ Silver* Ag+ 2+ Magnesium* Mg2+ Calcium* Ca2+ Stronium Sr2+ Barium* Ba2+ Zinc* Zn2+ Cadmium Cd2+ 3+ Aluminum Al3+ Anions 1- Hydride H- Flouride* F- Chloride* Cl- Bromide* Br- Iodide* I- 2- Oxide* O2- Sulfide* S2- 3- Nitride N3- *= most common We use roman numerals for metals that form more than one ionic compound o Suffix “-ous” for lower charges o Suffix “-ic” for higher charges Common Metals That form more than One Monatomic Ion: Element Ion Formula Systemic Name Common Name Chromium Cr2+ Chromium (II) Chromous Cr3+ Chromium (III) Chromic Cobalt Co2+ Cobalt (II) Co3+ Cobalt (III) Copper Cu+ Copper (I) Cuprous Cu2+ Copper(II) Cupric Iron Fe2+ Iron (II) Ferrous Fe3+ Iron (III) Ferric Lead Pb2+ Lead (II) Pb4+ Lead (IV) Mercury Hg_2 2+ Mercury (I) Mercurous Hg2+ Mercury (II) Mercuric Tin Sn2+ Tin (II) Stannous Sn4+ Tin(IV) Stannic A polyatomic ion stays together as a charged unit - When 2 or more of the same polyatomic ion are present in the formula unit, that ion appears in parentheses with the subscript written outside Most polyatomic ions are oxoanions (when an element, usually a nonmetal, is bonded to one or more oxygen atoms) Hydrates are ionic compounds that have water molecules in them Acids are hydrogen containing compounds - Acids, more specifically, are anions that have one or more hydrogen ions (H+) attached to them Binary Acids: Form when gaseous compounds dissolve in water Oxoacids: Similar to oxoanions - Suffix changes: o “-ate” turns into “-ic” o “-ite” turns into “-ous” Binary Covalent Compounds: Typically the combination of two nonmetals Hydrocarbons: Simplest organic compound containing only carbon and hydrogen Molecular Mass = Sum of atomic masses To Calculate formula mass with polyatomic ions, the number of atoms of each element inside parentheses is multiplied by the subscript outside the parenthesis Molecular Formula EX: H2O Structural Formula EX: H:O:H or H-O-H Heterogeneous Mixture: Has one or more visible boundaries between components Homogeneous Mixture: Has no visible boundaries cause each component is its own molecule Basic Separation Techniques: - Filtration: Often used to separate slid from liquid, it separates based on particle size - Crystallization: Separates based on the solubility of a substance - Distillation: separates based on a substances volatility, or tendency to become a gas - Chromatography: also separates based on differences in solubility
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