CH104chapter4StudySoup.pdf CH 104
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This 4 page Class Notes was uploaded by Regan Dougherty on Thursday October 1, 2015. The Class Notes belongs to CH 104 at University of Alabama - Tuscaloosa taught by Stephen Woski in Summer 2015. Since its upload, it has received 22 views. For similar materials see Introductory Chemistry in Chemistry at University of Alabama - Tuscaloosa.
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Date Created: 10/01/15
Thursday September 24 2015 CH 104 Chapter 4 Covalent Compounds Bonding between two nonmetals or a nonmetal and a metalloid involves sharing of pairs of electrons By sharing pairs of electrons both atoms have octets of valence electrons Bonding Patterns predicted number of bonds 8 number of valence of electrons Lewis structures electrondot structures for molecules show the locations of valence electrons lines represent bonds Drawing Lewis Structures arrange atoms with those bonded next to each other H and halogens on the periphery because they only form one bond count valence electrons place one bond between neighboring atoms give every atom an octet of electrons using lone pairs exception H can only have 2 electrons use multiple bonds when one atom does not have an octet Problems with Lewis Structures Resonance sometimes you can draw more than one lewis structure for the same compound there is a real structure that looks like a combination of the two hybrid structure Exceptions to the Octet Rule H only needs 2 valence electrons gives hydrogen a He configuration Li also has a He configuration Thursday September 24 2015 and Be2 not an octet but it is a noble gas configuration Boron is happy with 6 valence electrons H has zero electrons just a proton Naming Covalent Compounds 1 name first nonmetal by its name and the second using the suffix ide 2 add prefixes to show number of atoms in each element mono di tri tetra penta hexa hepta octa nona deca mono is usually omitted less electronegative element is usually first atom closest to metals will generally be first Electronegativity Not all atoms in covalent bonds share electrons equally In this case electrons are more closely associated with one atom than the other Electronegativity is measured in numbers Electronegativity increases as you go from left to right across the periodic table Electronegativity increases going up a group The element at the top of a group is going to be the most electronegative element nonpolar covalent bond electrons are shared equally this occurs between atoms of the same element or atoms with very similar electronegativity less than 05 units difference polar covalent bond electrons are unequally shared pulled towards the more electronegative element 05 19 units difference partial charge Thursday September 24 2015 ionic bond electrons are transferred from the less electronegative element to the more electronegative element greater than 19 units difference metal and nonmetal electronegativities for metals are lower than nonmetals Shapes of Molecules Linear If you have two molecules bonded to a central molecule they want to be as far apart as possible 180 degrees Trigonal Planar 3 molecules bonded to a central molecule as far apart as possible 120 degrees Tetrahedral 4 molecules bonded to a central molecule as far apart as possible 3D molecule 1095 degrees Lone pairs of electrons take up space just like bonds do Trigonal Pyramidal tetrahedral with a lone pair instead of a molecule on the top of the molecule 3 atoms and one lone pair 1095 Bentshape 2 atoms and two lone pairs 0 1095 Covalent bonding is the sharing of electrons but atoms do not always share equally Thursday September 24 2015 The more electronegative an element is the more it wants electrons How to decide if a bond is polar covalent or nonpolar covalent two atoms of the same element bonded to each other nonpolar covalent C H bonds nonpolar covalent We can assume that any other covalent bond is polar Carbon dioxide is not polar and water is polar Everything with a polar bond is a polar molecule
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