Ch 3 molecules compounds + chem eqns

Ch 3 molecules compounds + chem eqns - Ch. 3 (skip...

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Ch. 3 (skip 3.11—Ochem) Molecules + Compounds + Chemical Equations A. Elements vs. Compounds a. Properties of compounds are generally very different from properties of elements that compose them a.i. 2 H 2 (g) + O 2 (g) → 2 H 2 O (g) a.ii. Boiling point: H 2 (-253°C) O 2 (-183°C) H 2 O (100°C) a.iii. State at 25°C: gas gas liquid a.iv. Flammability rating: 4 3 0 B. 3.2 Chemical Bonds—result of interactions b/w charged particles (electrons + protons) a. Ionic Bonds a.i. transfer of electrons; resulting ions are attracted by electrostatic forces a.i.1. Metals typically give up their electrons; nonmetals typically take electrons a.i.2. Ionic bonds form compounds/salts ; cation = positive (metal); anion = negative (nonmetal) a.i.2.a. ionic compound in solid phase is composed of a lattice —regular 3-D array of alternating cations + anions a.i.3. b/w metal and nonmetal a.i.4. Formula: cation named 1 st , followed by anion (ex. NaCl) b. Covalent Bonds b.i. sharing of electrons—between 2 or more nonmetals b.ii. nonmetal and nonmetal b.iii. bonding atoms share some of their electrons—shared electrons interact with nuclei of both atoms, lowering the PE of system thru electrostatic interactions and forming covalent bond b.iii.1. Form molecular compounds , composed of individual covalently-bonded molecules b.iii.2. named by 1st most left in row, then column = alphabetically b.iv. Most EN atom = fluorine (as you go up a group EN increases, as you go right in a period EN increases b.v. Nonmetals have more EN than metals C. 3.3 Representing Compounds: Chemical Formulas + Molecular Models a. chemical formula : indicates the elements present in compound + relative # of atoms/ions in each
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a.i. normally list the more metallic (positively charged) elements first, followed by less metallic (more negatively charged) elements b. Types of Chemical Formulas b.i. empirical formula : gives relative number of atoms of each element in a compound b.i.1. ionic formulas are empirical formulas since salts are composed of repeating structures, not discrete molecules b.ii. molecular formula : gives actual number of atoms of each element in a molecule of a compound
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This note was uploaded on 02/17/2012 for the course CHEM 105ALg taught by Professor Bau during the Spring '07 term at USC.

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Ch 3 molecules compounds + chem eqns - Ch. 3 (skip...

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