Chapter 3: Reading Guide
Chapter 3: Reading Guide CHEM-111
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This 5 page Class Notes was uploaded by Madelyne Crawford on Monday September 12, 2016. The Class Notes belongs to CHEM-111 at Campbell University taught by Dr. Kesling in Fall 2016. Since its upload, it has received 7 views. For similar materials see General Chemistry in Chemistry at Campbell University.
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Date Created: 09/12/16
Chapter 3: Molecules, Compounds, and Chemical Equations Section 3.1: Hydrogen, Oxygen, and Water When two or more elements combine, forming a compound, a completely new and different substance results o Ex: hydrogen (explosive gas) and oxygen (key to combustion) combine to produce water (very different than hydrogen and oxygen) Know the difference between compound and mixture!!!: compound is combinations of elements in definite proportions and mixtures are random proportions that do not matter Section 3.2: Chemical Bonds Chemical bonds hold the atoms together that compose compounds o Why do bonds form? - attractions between protons and electrons Two types of chemical bonds: o Ionic- occur between metals and nonmetals (involves the TRANSFER of electrons between atoms) o Covalent- occur between two or more nonmetals (involves sharing of electrons between atoms) Know that metals usually lose electrons and nonmetals gain electrons Know that cations are positively charged ions and anions are negative Ionic bond- formed by the oppositely charged cations and anions attracting one another through electrostatic forces Ionic compound- the result of ionic bonds; made up of a lattice (a 3D array) of alternating cations and anions Covalent bond- formation: when two nonmetals bond together, the electrons do not transfer; instead, they share some of each of their electrons; shared e- have lower potential energy because they have interacted with the nuclei of both atoms Molecule- composed by the covalently bound atoms in a covalent bond Molecular compounds- covalently bonded compounds o WHY? Because each molecule is dependent on all the others Section 3.3: Representing Compounds- Chemical Formulas and Molecular Models Chemical formula- fastest and simplest way to represent a compound; identifies the elements in the compound and number of atoms or ions in each element Chemical formulas- characterized into three kinds: o Empirical formula- tells the relative # of atoms of element within a compound; voices the least info o Molecular formula- actual # of atoms of each element in a molecule of a compound o Structural formula- uses lines to represent covalent bonds and shows how atoms in a molecule connect or bond to one another; voices most of the info Can also be used to indicate some of the molecule’s geometry Can also show different types of bonds in molecules Molecular model- a more accurate way to specify a compound Ball-and-stick molecular model- atoms=balls, bonds=sticks; used to reflect the molecule’s shape through connections Space-filling molecular model- atoms fill up the space between each other to more accurately show the best guess for how a molecule may look if it were a visible size Tetrahedron- formed by four hydrogen atoms Section 3.4: An Atomic-Level View of Elements and Compounds Atomic elements- found in nature with their basic units being single atoms o Ex: helium is made up of helium atoms Molecular elements- not usually found in nature with their basic units being single atoms o They exist as molecules- two or more atoms bonded together chemically o Diatomic molecules- hydrogen is made up of H2 molecules o Polyatomic molecules- phosphorous exists as P4 molecules o Usually made up of two or more covalently-bonded nonmetals o Ionic compounds- usually made up of metals ionically bonded to nonmetals Formal unit- basic unit of an ionic compound; smallest neutral group of ions Polyatomic ion- ions made up of two or more atoms Section 3.5: Ionic Compounds- Formulas and Names Formulas for ionic compounds can be deduced because: o Charge-neutral o Most elements form just one ion with a predictable charge Common names- nicknames that are learned because of familiarity o Ex: NaCl= table salt Systematic names- determined from chemical formulas; developed by scientists for different kinds of compounds Steps in naming an ionic compound: Identify it as an ionic compound (composed of metals and nonmetals!!!) o Types of ionic compounds: 1) a metal that has a charge that does not vary from compound to compound and 2) contains metal with a charge that is different from compound to compound (most often are transition metals) Binary compounds- only have two different elements o Name: name of cation (metal) + base name of anion (nonmetal) + “-ide” o More than one cation is named: name of cation + charge of cation in Roman numerals + base name of anion o Naming ionic compounds with polyatomic ions- use same strategy but ass polyatomic ion’s name whenever it occurs Oxyanions- anions that have oxygen and another element o If there are just two ions, the one with more O atoms has –ate ending and the one with fewer has –ite ending o More than two: prefixes hypo- (less than) and per- (more than) are used Hydrates- have a specific # of water molecules associated with each formula unit o Waters of hydration- the seven water molecules associated with each formula unit; can be removed with heat Cannot be determined from constituent elements because the same combo of elements may form from different molecular compounds How to name: prefix + name of first element + prefix + base name of second element + -ide Prefixes given to each element tell the number of atoms: o Mono= 1 o Di= 2 o Tri= 3 o Tetra= 4 o Penta= five Acids- molecular compounds that put out hydrogen ions when dissolved in water o Characterized by sour taste and ability to dissolve many metals o Ex: hydrochloric acid in our stomach o Two types of acids: Binary- composed of hydrogen and a nonmetal (name: hydro + base name of nonmetal + acid) Oxyacids- contain hydrogen and an oxygen (Name: ending with –ate is base name + -ic + acid and ending with –ite is base name of oxyanion + -ous + acid Section 3.7: Summary of Inorganic Nomenclature Having to name a compound without knowing what category it is part of How to use the chart (find chart in book pg. 106) o Determine the kind of compound you are attempting to name o Figure out whether the metal in the compound forms just one kind of ion or more than one kind o Name the compound based on the blocks at the end of the path in the chart Section 3.8: Formula Mass and the Mole Concept for Compounds Formula mass- defines the average mass of a molecule of a compound o = (# atoms of 1 element in chemical formula X atomic mass of 1 element) + (# atoms of second element X atomic mass of 2 nd element) + … o the molar mass of a compound is numerically equal to its formula mass Section 3.9: Composition of Compounds mass percent composition- used to express how much of an element is in a certain compound o = (mass pf element in one mole of compound / mass of 1 mole of the compound) X 100% mass percent composition is a conversion factor between mass of element and mass of compound always remember that chemical formula only tells the relationship between the amounts (in moles), not the masses Section 3.10: Determining a Chemical Formula from Experimental Data the molecular formula of a compound can be found from the empirical formula if the molar mass is also known o molecular formula= empirical formula X n (n= 1, 2, 3….) empirical formula molar mass- sum of the masses of all the atoms in the empirical formula o molar mass= empirical formula molar mass X n if the value of n is the same: o n= molar mass/ empirical formula molar mass combustion analysis- another way to figure out formulas for unknown compounds; unknown compound goes through combustion in presence of pure oxygen and then samples are weighed Section 3.11: Writing and Balancing Chemical Equations combustion analysis employs a chemical reaction- process where one or more substances are converted into one or more different ones o ex: water is formed through reaction between hydrogen and oxygen combustion reaction- specific type of chemical reaction where a substance combines with oxygen to form one or more oxygen- containing compounds o emit heat, critical for supplying energy needs chemical equation- represents a chemical reaction reactants- substances on the left side of the equations products- substances on the right balance an equation- change the coefficients (#s in front of chemical formulas, not the subscripts) to make the # of each atom on left equal to number on the right o matter has to be conserved- new atoms do not form during reactions Guidelines for balancing equations: o 1. Write a skeletal equation; write formulas for each reactant and product o 2. Balance atoms that are in more complex substances first; balance atoms in compounds before atoms in pure elements o 3. Free elements get balanced last; adjust their coefficients o 4. Clear coefficient fractions o 5. Make sure the equation is balanced by adding the total # of each atom on both sides of equation Section 3.12: Organic Compounds organic compounds- made up of carbon and hydrogen and some other elements: nitrogen, oxygen, sulfur o common in everyday substances (like perfume and spices) carbon is the backbone of millions of different chemical compounds (forms bonds with itself) hydrocarbons- organic compounds that are made up of only carbon and hydrogen o common fuels, like gasoline and natural gas o alkanes- hydrocarbons containing only single bonds o alkenes- double bonds o alkynes- triple bonds functionalized group- characteristic atom or group of atoms o functionalized hydrocarbons are hydrocarbons in which functionalized groups are incorporated into the hydrocarbon o ex: alcohols family- a group of organic compounds with the same functional group Quizlet!! https://quizlet.com/150669212/chem-chapter-3-flash-cards/?new
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