How many of the following statements are true? • Formal charge can be used to pick the best Lewis structure amongst 2 choices. • For a species having three resonance structures, it is best to think of the species to exist as each of these structures one- third of the time, and switching between those three structures • Resonance structures involve changes to the sigma bonds. 02

Decide whether this proposed Lewis structure is reasonable. proposed Lewis structure Is the proposed Lewis structure reasonable? Yes. No, it has the wrong number of valence electrons. : Z: : 0: N O C1: The correct number is: ☐ - No, it has the right number of valence electrons but doesn't satisfy the octet rule. The symbols of the problem atoms are:* ☐ * If two or more atoms of the same element don't satisfy the octet rule, just enter the chemical symbol as many times as necessary. For example, if two oxygen atoms don't satisfy the octet rule, enter "0,0". X

How many covalent bonds and how many ionic bonds are there in the molecular structures below? Please note that a pair of cation (+) and anion (-) form ONE ionic bond, and that a double bond counts for TWO covalent bonds.

ed Lewis structure H-H-0 : Cl H10: Η HO H :0: U: :: + C-Cl: Is the proposed Lewis structure reasonable? Yes. No, it has the wrong number of valence electrons. The correct number is: No, it has the right number of valence electrons but doesn't satisfy the octet rule. The symbols of the problem atoms are: * Yes. No, it has the wrong number of valence electrons. The correct number is: No, it has the right number of valence electrons but doesn't satisfy the octet rule. The symbols of the problem atoms are: * Yes. No, it has the wrong number of valence electrons. The correct number is: No, it has the right number of valence electrons but doesn't satisfy the octet rule. The symbols of the problem atoms are: *

What are the formal charges of the resonance structure :C=S:=S::

Write the Lewis structure for each molecule/ion. NO2-

COMPARING LEWIS STRUCTURES TO2/S02 | =N = :o: Enter the overall charge for each substance. For a non-zero charge greater than one, enter the number first and then sign. Calculate the overall charge by summing the formal charge on each atom in the species. :ö:

Writing Lewis Structures Many Lewis structures can be drawn by inspection but a system helps to draw the more complex ones. One approach is too : 1. Draw a skeleton of the major (non-hydrogen) atoms with single bonds ( lines) between each one. Several general considerations will help produce a valid skeletal diagram. normal covalency number or number of bonds that each atom forms. Consider the For the major atoms these are : Element Bond(s) HYDROGEN 1 BORON 3 ALUMINUM 3 CARBON | 4 NITROGEN 3 OXYGEN 2 HALOGENS 1 Also note that hydrogen, boron, aluminum and the halogens seldom form multiple bond.

Decide whether these proposed Lewis structures are reasonable. proposed Lewis structure :: : Cl - : 0: :0: :Z: C. C= : Z: N N Cl: Is the proposed Lewis structure reasonable? Yes. No, it has the wrong number of valence electrons. The correct number is: No, it has the right number of valence electrons but doesn't satisfy the octet rule. The symbols of the problem atoms are:* Yes. No, it has the wrong number of valence electrons. The correct number is: No, it has the right number of valence electrons but doesn't satisfy the octet rule. The symbols of the problem atoms are:* 0 Yes. No, it has the wrong number of valence electrons. The correct number is: No, it has the right number of valence electrons but doesn't satisfy the octet rule. The symbols of the problem atoms are:* * If two or more atoms of the same element don't satisfy the octet rule, just enter the chemical symbol as many times as necessary. For example, if two oxygen atoms don't satisfy the octet rule, enter "0,0". X 5

Determine the formal charge for the atom indicated in the structures below. ASSUME that the structures are drawn correctly and that you do not have to change them due to formal charge issues. The external atom in this structure. :O: :O! Ar 11 :0: The central atom in this structure. = :0: (1 Si = : 0: 2- 1. +1 2. +2 3. +3 4. 0 5. -3 6.-2 7. -1