Download Lewis Structure Tutorial and more Lecture notes Chemistry in PDF only on Docsity!
1 Lewis Structure Tutorial 10.7.00 6:16 PM
Drawing Lewis Structures
A Tutorial on Writing Lewis Dot Structure
Drawing Lewis Structures Drawing Lewis Structures
A Tutorial on Writing Lewis Dot Structure A Tutorial on Writing Lewis Dot Structure
Dr. Fred Omega Garces Dr. Fred Omega Garces
Chemistry 100Chemistry 100 Miramar CollegeMiramar College
Lewis Structure by Bond Determination Lewis Structure by Bond Determination
- Know how to determine the valence electron for all elements.
- (Connectivity) From the Chemical Formula, determine the atom connectivity for the structure. i. Given a chemical formula, ABn, A is the central atom and B flanks the A atom. i.e., NH 3 , NCl 3 , NO 2. In these examples, N is central in the structure. ii. H and F are never central atoms.
- (# of Bond) Determine the number of bonds in the compound, by calculating the theoretical Octet electrons (Oe) minus the total valence electrons (TVe). O-e is the theoretical number of electrons necessary for each atom in the structure to obtain a Noble Gas electron configuration, while TVe is the actual number of total valence electron for each atom in the structure.
- (Remaining e-) Calculate the number of remaining electrons in the compound by taking the total valence electron (TVe) minus the number of electrons that was used to form bonds. Complete Lewis structure by drawing atomic connectivity. Write bonds in the structure and the place remaining electrons to selected atoms in the structure to give each atom an octet. Keep in mind that the H-atom is satisfied with 2 electrons.
3 Lewis Structure Tutorial 10.7.00 6:16 PM
Valence electrons for Elements Valence electrons for Elements Recall how to determine the valence electron for the elements basedRecall how to determine the valence electron for the elements based on the elements position on the periodic table.on the elements position on the periodic table.
Lewis Dot SymbolLewis Dot Symbol
Valence electrons and number of bondsValence electrons and number of bonds
Recall the number of bonds at atom prefers depending Recall the number of bonds at atom prefers depending on the number of valence electronson the number of valence electrons
X
Family # Covalent Bonds*
Halogens F, Br, Cl, I
Calcogens O, S
Nitrogen N, P
Carbon C, Si
O
N
C
1 bond1 bond^ oftenoften
2 bond2 bond^ oftenoften
3 bond3 bond^ oftenoften
4 bond4 bond^ alwaysalways
In general, these are the number of bonds formed by these atoms.
7 Lewis Structure Tutorial 10.7.00 6:16 PM
Setting up the bond table requires the chemical formula,Setting up the bond table requires the chemical formula, and determining the number of electrons around each atom.and determining the number of electrons around each atom. A) Chemical Formula I.e.,A) Chemical Formula I.e., HNOHNO 33 B) Oe - Octet Electrons (This is always either 8 (or 2 for H)B) Oe - Octet Electrons (This is always either 8 (or 2 for H) C) Tve - Total Valence Electron.C) Tve - Total Valence Electron.
Setting up Bond Table Setting up Bond Table
ChemFormula Octet e- Tot Val e- HNOHNO 33 OeOe TveTve H N O
1 x 2 = 2 1 x 8 = 8 3 x 8 = 24
1 x 1 = 1 1 x 5 = 5 3 x 6 = 18 34 24
Note this receipt works only if the chemical specie obeys the octet rule. For chemical specie which violates the octet rule, this method must be modified.
Note this receipt works only if the chemical specie obeys the octet rule. ForNote this receipt works only if the chemical specie obeys the octet rule. For chemical specie which violates the octet rule, this method must be modified.chemical specie which violates the octet rule, this method must be modified.
After setting up the bond table, calculate theAfter setting up the bond table, calculate the^ number ofnumber of bondsbonds in the chemical specie and the number of electrons.in the chemical specie and the number of electrons. TheThe^ remaining electronsremaining electrons^ are place around the atoms in theare place around the atoms in the chemical specie such that each atom obeys the octet rulechemical specie such that each atom obeys the octet rule
Calculating the Number of Bonds and Calculating the Number of Bonds and the Remaining electronsthe Remaining electrons
HNO HNO 33 OeOe TveTve # Bonding e# Bonding e-- Bond Table
of Bonds
Remaining e-
34 - 24 = 10 10/2 = 5 Tve(24) - electrons in Bond (10) = 14
9 Lewis Structure Tutorial 10.7.00 6:16 PM
Chemical formula: 1) Chemical formula: 2) Atomic sequence:2) Atomic sequence: HHNNOO 33
Number of bonds 3) Number of bonds = 5= 5
Remaining electrons = 144) Remaining electrons= 14
Lewis Structure with 5 bonds:5) Lewis Structure with 5 bonds:
Complete Lewis Structure6) Complete Lewis Structure withwith (^1414) remaining electronsremaining electrons
Putting it TogetherPutting it Together
HH
OO NN OO
OO
HH
OO NN^ OO
OO
HH
OO NN OO
OO
Lewis Dot Structure of CO Lewis Dot Structure of CO 22 by Bonds Tableby Bonds Table
B. Calculate the number of bonds in compound B. Calculate the number of bonds in compoundstructure.structure.
bonds = (Oe - TVe)
2 = (24- 16) = 8 = 4 bonds 2 2 C. Calculate the remaining electrons to add to C. Calculate the remaining electrons to add to structure to complete Lewis dot structure.structure to complete Lewis dot structure. Remaining e- = TVe - e-^ used in bonding. = 16 - 8 = 8 e-Remaining Writing Lewis Structure: First determine atom connectivity keeping in mind that H and F can never be central atoms. Generally when given the formula, ABn, A is the central atom in the structure (but not always), and B atoms flank the central atom. Next use information from the above calculations. Total of 16e- in CO 2 , of which 8 electrons are used to form 4 bonds and 8 remaining electrons are used to complete Lewis structure. O C O
- Place the remaining 8 electrons in the structure to complete the Lewis Structure
A. Calculate Octet electrons (Oe-) andA. Calculate Octet electrons (Oe-) and Total Valence electrons to determineTotal Valence electrons to determine number of bondsnumber of bonds CO 2 Oe TVe 1 C 1•(8)= 8 1•(4) = 4 2 O 2•(8)=16 2•(6)= Chg 24 16
1,2. Write atom connectivity for CO 2.
3,4,5. Draw the four bonds in the structure.
O C O O C O
SummarySummary Summary
Lewis Structure Determination:Lewis Structure Determination:
- • Molecular FormulaMolecular Formula
- • Atomic Sequence (H and F are terminal)Atomic Sequence (H and F are terminal)
- • Determine the # of bondsDetermine the # of bonds
Oe Oe--^ and TVeand TVe--
of Bonds = (Oe - TVe # of Bonds = (Oe - TVe--) / 2) / 2
- • Determine remaining electronsDetermine remaining electrons
Re = (TVe Re = (TVe--) - (# e) - (# e--^ in bonding)in bonding)
- • Make sure all atoms satisfy octet rule (Except H whichMake sure all atoms satisfy octet rule (Except H which
is satisfied with 2 electronsis satisfied with 2 electrons)
