DOC PREVIEW
NCSU CH 101 - Molecular Structures

This preview shows page 1-2 out of 5 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 5 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 5 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 5 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

CH 101 1st Edition Lecture 12Outline of Last Lecture I. PolarityII. Molecular BondsA. Formal ChargeIII. Lewis StructuresIV. Drawing out Lewis StructuresOutline of Current Lecture I. Equivalent Resonance StructuresII. Preferred Resonance Structures III. Molecular StructureIV. Bond OrderA. Finding the Oxidation State using the Electron Counting MethodCurrent LectureV. Equivalent Resonance Structures- Equivalent resonance structures occur when a molecule has the same elements surroundingit, this means that if there is a double bond that needs to be placed in the Lewis structure it doesn’t matter which bond the double bond is placed between. This occurs in molecules likeCO32- because when you look at the Lewis structure you see that there is a double bond that can be place between any of Carbon and Oxygen atoms. Here are the three equivalent resonance structures of CO32-.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.VI. Preferred Resonance Structures - Preferred resonance structures occurs when you create different Lewis structures that AREN’T the same because the central atom is bonded to different types of elements like in CHO2-. Find the preferred resonance structure by looking for the structure that does not have a charge, and if it does, the charge is on the most electronegative element. Ex)What is the preferred Lewis structure for the molecule SCN-?ER = 24, VE = 16, SP = 4, LP = 4 <-Determine your Lewis structure.Using the information found about the Lewis structure of SCN- there are three structures that can be drawn. Analyze the three structures and determine which one is preferred by finding the formal charges (which has thenegative charge on the most electronegative atom)In A, the formal charges are S1+ and N2-In B, the formal charge is S1-In C, the formal charge is N1- <- Using the formal charge, Use that fact that the electronegativity of S is greater than N help you decide the preferred Lewis structure.<- B is the preferred Lewis structure for SCN-.VII. Molecular Structure The molecular structure is determined by the amount of bond regions there are and if there is a lone pair on the center atom. The lone pair/pairs attached to the center atom are known as dipoles and they distort the angle of the bonds by pushing the angles closer together.Electron RegionsLone pairs around center atomBond AngleName of shape Visual2 0 180oLinear2 1 <120oBent3 0 120oTrigonal Planar3 1 <109oTrigonal Pyramidal4 2 <109oBent/Angular4 0 109oTetrahedralVIII. Bond Order- The bond order can be calculated by dividing the amount of bonds in the molecule by the amount of bond regions (# of total bonds/ # of bond regions). DON’T FORGET to draw in your lone pairs because they count as bond regions if they are around the central atom.- When you are trying to determine the bond order of a particular part of a molecule, first look at the bond then determine if the atoms bonded are bonded to the same element inanother bond like O – C – O. If she points out the bond highlighted in red and asks for the bond order, you would see if the carbon in bonded to another oxygen or if the oxygen is attached to another carbon. Since the carbon is attached to another oxygen the number of bonds is 2 and the number of regions is 2, therefore the bond order is 2/2=1.Ex) Find the bond order of the molecule CO32-.ER= 32 VE= 24 SP= 4 LP= 8 <- Determine the Lewis structure of CO32-<- Here is the Lewis structure, to find the bond order you must find the number of binds andthe number of bond regions.Bond # = 4, Bond regions = 3 <- You can see that although there are 4 bonds, there are only 3 regions because of the double bond.4/3 <- Plug into the equation (bond#/bond regions) to find that the bond order is 4/3.A. Finding the Oxidation State using the Electron Counting Method- In chapter five, the counting method was introduced to find the oxidation state of anatom within a molecule. The oxidation state is found by finding the valence electronsof the atom and subtracting the number of possessed electrons (VE-PE=oxidation state). When finding the possessed electrons, use the electronegativity of the atoms to determine which atom takes the electrons.- The atom with the higher electronegativity possess both of the electrons in the bond- If the atoms bonded are the same elements, each atom gets one electron out of the pair.Ex)Find the oxidation state of the CA carbon in the molecule C2HOF2using the electron counting method.<- Here is the Lewis structure for the molecule C2HOF2VE for CA is 4<- You can reference the Lewis structure or the periodic table to determine that the valence electrons for carbon is 4Electronegativity of F > C > H <- Look at the periodic table to determine which atoms have the higher electronegativity in each bond, this will determine the amount of possessed electrons an atom has because the more electronegative atom gets both the electrons. PE for CA is 1<- Fluorine take both the electrons in the bond with Carbon but carbon possesses one electron in its bond with Carbon4 – 1 = +3<- Plug into VE – PE = oxidation state to get +3 as the oxidation state of


View Full Document

NCSU CH 101 - Molecular Structures

Download Molecular Structures
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Molecular Structures and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Molecular Structures 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?