CH301 - chapter 2 notes

CH301 - chapter 2 notes - 1 General Chemistry I Chapter 2...

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1 General Chemistry I Chapter 2 2-1 Atoms and Molecules Dalton’s Atomic Theory - 1808 Five postulates 1. An element is composed of extremely small, indivisible particles called atoms. 2. All atoms of a given element have identical properties that differ from those of other elements. 3. Atoms cannot be created, destroyed, or transformed into atoms of another element. 4. Compounds are formed when atoms of different elements combine with one another in small whole- number ratios. 5. The relative numbers and kinds of atoms are constant in a given compound. The atom and the fundamental particles (Table 2.1) p + , n o , and e Atomic number (Z) Z = number of p + in the nucleus of an atom of a particular element Periodic table is arranged by increasing atomic number Molecule: smallest particle of an element or compound that can stably exist. Held together by sharing e (Covalent bonding). Nonmetals + nonmetals. ± H 2 ± O 2 ± S 8 ± H 2 O ± CH 4 ± C 2 H 5 OH diatomic elements: Br I N Cl H O F Î Br 2 I 2 N 2 Cl 2 H 2 O 2 F 2 polyatomic elements: P 4 S 8 compounds: H 2 O, H 2 O 2 , CO , CO 2 , CH 4 , CH 3 CH 2 CHOH
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2 2-2 Chemical Formulas Chemical formula shows the chemical composition of the substance. ± ratio of the elements present in the molecule or compound He, Au, Na – monatomic elements O 2 , H 2 , Cl 2 – diatomic elements O 3 , S 4 , P 8 - more complex elements H 2 O, C 12 H 22 O 11 – compounds ² Substance consists of two or more elements Compound 1 Molecule Contains HCl 1 H atom & 1 Cl atom H 2 O 2 H atoms & 1 O atom NH 3 1 N atom & 3 H atoms C 3 H 8 3 C atoms & 8 H atoms Allotropes of elements: O 2 vs. O 3 Î elements that exist in more that one molecular form. Nobel gases Î only elements that can exist as single atoms 2-3 Ions and Ionic Compounds (Salts, formula units) Ions are atoms or groups of atoms that possess an electric charge. Two basic types of ions: Positive ions or cations Ionic compounds are formed from metals and nonmetals. Cations: positively charged atoms (metals) Group IA metals Î + 1 charge Li + Na + K + Rb + Cs + Group IIA metals Î +2 charge Mg 2+ Ca 2+ Sr 2+ Ba 2+ Group IIIA metals Î +3 charge Al 3+ Ga 3+ Anions: negatively charged atoms (nonmetals) Group VIIA nonmetals Î 1 charge F Cl Br
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This note was uploaded on 06/19/2008 for the course CH 301 taught by Professor Fakhreddine/lyon during the Spring '07 term at University of Texas at Austin.

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CH301 - chapter 2 notes - 1 General Chemistry I Chapter 2...

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