Chapter%202%20Outline - Chemistry 101 Vandan Desai Chapter...

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Chemistry 101 Vandan Desai P a g e | 1 Chapter 2: Compounds and Chemical Reactions (Lecture Outline) -------------------------------------------------------------------------------------------------------------------------- Elements combine to form compounds in two ways… o Sharing of electrons between atoms s Produces discrete, electrically neutral particles called molecules s Molecular compounds are composed of molecules o Transfer of one or more electrons from one atom to another s Produced electrically charged particles called ions s Ionic compounds are composed of ions I. Elements combine to form compounds A. Properties of substances present prior to reaction differ quite a lot from the properties of those present afterwards B. Chemical formulas specify the composition of a substance 1. Chemical formulas – tells which elements are present and how many of each atom is present 2. For free element (one that is not combined with another element in a compound) simply use the chemical symbol 3. Diatomic molecules – molecules composed of two atoms each Hydrogen, Nitrogen, Oxygen, Flourine, Chlorine, Bromine, and Iodine H ave o F ear O f I ce C old B ear C. Compounds have formulas that describe their compositions 1. Most important characteristic of a compound’s formula is that it specifies the composition of the substance 2. When more than one atom of an element present, the number of atoms is given by a subscript 3. For more complicated compounds, formulas sometimes contain parentheses 4. Hydrates – crystals that contain water in fixed proportions Water molecules not held very tightly; can be driven off thru heat II. Chemical equations describe what happens in chemical reactions A. Chemical equation – describes what happens when a chemical reaction occurs B. Reactants b Products 1. Reactants – substances present before the reaction begins 2. Products – substances present after the reactions ends 3. Arrow – “reacts to yield” C. Coefficients are written in front of formulas to balance an equation 1. Coefficients – indicate the number of molecules of each kind among the reactants and products 2. Balanced equation – conform to the law of conservation of mass; same number of atoms of each kind present before and after the reaction D. The states of reactants and products can be specified in a chemical equation
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This note was uploaded on 03/13/2008 for the course SPEECH 101 taught by Professor Angelakatenkamp during the Spring '08 term at UMBC.

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Chapter%202%20Outline - Chemistry 101 Vandan Desai Chapter...

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