Formal Charge and Lewis Structures

The video tutorial covers the basics of drawing Lewis structures, emphasizing the octet rule. It introduces formal charges as a tool to determine the best Lewis structure when multiple valid structures exist. The concept of dominant Lewis structures is explained, highlighting the importance of formal charges and electronegativity. Resonance structures are introduced, clarifying common misconceptions. Finally, exceptions to the octet rule, such as odd numbers of electrons and expanded octets, are discussed.

What is the primary rule used to determine the correctness of a Lewis structure?

• The number of atoms in the molecule

• The octet rule

• The molecular weight

• The color of the molecule

How is a formal charge defined?

• The charge based on the number of neutrons

• The charge based on the number of protons

• The actual charge of the atom

• The charge an atom would have if all atoms had the same electronegativity

When calculating formal charge, how are electrons in a bond assigned?

• All electrons are assigned to the more electronegative atom

• All electrons are assigned to the less electronegative atom

• None of the electrons are assigned

• Half of the bonding electrons are assigned to each atom

What is the formal charge of carbon in the dominant CO2 Lewis structure?

• -1

• 0

• +2

• +1

In a dominant Lewis structure, where should the negative formal charge reside?

• On the more electronegative atom

• On the less electronegative atom

• On the central atom

• On the atom with the most bonds

What is a common misconception about resonance structures?

• They exist as separate forms half the time

• They are not valid Lewis structures

• They only occur in ionic compounds

• They exist as a blend of all possible structures

What is the nature of O3's resonance structure?

• It has one double bond and one single bond

• It is a blend of two structures

• It exists only as a single structure

• It has two double bonds

Which element is likely to have less than an octet of valence electrons?

• Nitrogen

• Boron

• Oxygen

• Carbon

Why can elements in the third period have more than an octet of valence electrons?

• They have more protons

• They have a d orbital available for bonding

• They have a larger atomic radius

• They are more electronegative

What is an example of a molecule with an odd number of valence electrons?

• H2O

• O3

• CO2

• NO