University:
San Jose State University
Course:
CHEM 145 | Inorganic Chemistry
Academic year:

2023
Views:

212

Pages:

6
Author:

96XGbl6o

Chapter: 12 Molecular Structure: 3-Dim arrangement of atoms in a molecule. In Lewis Symbols: The number of dots = number of valance electrons = column number (main group/Periodic table) - Writing Lewis Structure: (i.e.: PO2F 2) 1) Draw a skeleton structure of molecule (The less electronegative element is the central atom) (H is always a terminal atom) Example: F F P - O O 2) Determine the total number of valence electrons in the structure. Element/Charge P O O F F 0ne negative charge Total Valence ē 5 6 6 7 7 1 32 3) Deduct the 2 valance electrons for each bound in step 1. Distribute the remaining electrons as unshared pairs. Each atom has 8 electroins if possible. If there are too few electroins to give octet rule, convert single bonds to multiple bonds. F - O P F O 12 lone pairs 4 electron pairs as 4 single bonds ( ) Jupiter’s atmosphere contains small amount of compounds methane, CH4, acetylene, C2H2 , and phosphine, PH3. What are the Lewis structures of these molecules? P C H H H H C H H H C C H P H H The three-dimensional arrangement of atoms in a molecule is called molecular structure. A bond distance: Distance between the nuclei of two bonded atoms along a straight line joining the nuclei (unit: picometer: 10-12 m). A bond angle: The angle between any two bonds that include a common atom. To predict approximate bond angles around a central atom in a molecule by using VSEPR theory: Valance Shell Electron-Pair Repulsion The electrostatic repulsion of bond pair and unshared pairs electrons is reduced to a minimum when they occupying region of space as far from each other as possible. 180° High electrostatic repulsion Low electrostatic repulsion 120° Polarity of bonds & polarity of molecules: Polar bond: A bond in which bonding electrons are shared unequally. Low High Electronegativity Electronegativity A polar molecule has unbalanced polar covalent bonds. O C O δO H δ+ H Organic Chemistry = Chemistry of Carbon compounds Hydrocarbons: compounds made up of C & H Name # Of C Methane 1 Ethane 2 Propane 3 Butane 4 Alkane n Formula CH4 C2H6 C3H8 C4H10 Isomers: same formula but different arrangements of atoms. (n-butane, isobutene) C C C C C C C C CnH(2n+2) There are 300,000 isomeric structures for C20H42 !! C is able to form four covalent bonds with other atoms. Alcohols: C O H i.e.: methanol, ethanol, and propanol Ethers: C O C i.e.: dimethyl ether O Carboxylic acids C i.e.: formic acid, acetic acid O H

CHEM 145 Inorganic Chemistry, Chapter 12 Notes

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