2 Lewis Structures Find your element on the periodic table. Determine the number of valence electrons.This is how many electrons you will draw.
3 Lewis Structures Find out which group (column) your element is in. This will tell you the number of valence electrons your element has.You will only draw the valence electrons.
4 Except for He, it has 2 electrons Group 2 = 2 electrons 3, 4, 5, 6, 7Each column is called a “group”Each element in a group has the same number of electrons in their outer orbital, also known as “shells”.The electrons in the outer shell are called “valence electrons”
5 C Lewis Structures Write the element symbol. Carbon is in the 4th group, so it has 4 valence electrons.Starting at the right, draw 4 electrons, or dots, counter-clockwise around the element symbol.C
6 C Lewis Structures Check your work. Using your periodic table, check that Carbon is in the 4th group.You should have 4 total electrons, or dots, drawn in for Carbon.C
7 C Lewis Structures On your worksheet, try these elements on your own: PCaArClAlC
8 H Lewis Structures On your worksheet, try these elements on your own: PCaArClAlH
9 P Lewis Structures On your worksheet, try these elements on your own: CaArClAlP
10 Ca Lewis Structures On your worksheet, try these elements on your own: PCaArClAlCa
11 Ar Lewis Structures On your worksheet, try these elements on your own: PCaArClAlAr
12 Cl Lewis Structures On your worksheet, try these elements on your own: PCaArClAlCl
13 Al Lewis Structures On your worksheet, try these elements on your own: PCaArClAlAl
14 Octet RuleRemember…Most atoms form bonds in order to have 8 valence electrons.
15 F B F F H O H N O F F F S F Very unstable!! A. Octet Rule Exceptions: Hydrogen 2 valence e-Groups 1,2,3 get 2,4,6 valence e-Expanded octet more than 8 valence e- (e.g. S, P, Xe)Radicals odd # of valence e-C. Johannesson
16 Drawing Lewis Diagrams Find total # of valence e-.Arrange atoms - singular atom is usually in the middle.Form bonds between atoms (2 e-).Distribute remaining e- to give each atom an octet (recall exceptions).If there aren’t enough e- to go around, form double or triple bonds.
17 Drawing Lewis Diagrams CF41 C × 4e- = 4e-4 F × 7e- = 28e-32e-FF C F- 8e-24e-
18 B. Drawing Lewis Diagrams BeCl21 Be × 2e- = 2e-2 Cl × 7e- = 14e-16e-Cl Be Cl- 4e-12e-
19 B. Drawing Lewis Diagrams CO21 C × 4e- = 4e-2 O × 6e- = 12e-16e-O C O- 4e-12e-
20 Polyatomic Ions To find total # of valence e-: Add 1e- for each negative charge.Subtract 1e- for each positive charge.Place brackets around the ion and label the charge.
21 O O Cl O Polyatomic Ions ClO4- 1 Cl × 7e- = 7e- 4 O × 6e- = 24e- 31e-
22 H H N H Polyatomic Ions NH4+ 1 N × 5e- = 5e- 4 H × 1e- = 4e- 9e- - 1e-
23 Resonance StructuresMolecules that can’t be correctly represented by a single Lewis diagram.Actual structure is an average of all the possibilities.Show possible structures separated by a double-headed arrow.C. Johannesson
24 Resonance StructuresSO3OO S OOO S OOO S OC. Johannesson