Q: Which of the following is the correct formula for calculating the formal charge on an atom?

$$\text{Formal charge} = \text{Number of valence electrons in free atom} - \frac{\text{Number of bonding electrons}}{2} - \text{Number of nonbonding electrons}$$

Question 1

Which of the following molecules has a net dipole moment of zero?

Accepted Answer

Carbon dioxide ($$\mu = 0)$$

Question 2

What is the formal charge on the oxygen atom in dimethyl sulfoxide ($$\mathrm{(CH_3$)_2SO}$$)?

Accepted Answer

$$-1$$

Question 3

Which of the following is the correct formula for calculating the formal charge on an atom?

Accepted Answer

$$	ext{Formal charge} = 	ext{Number of valence electrons in free atom} - \frac{	ext{Number of bonding electrons}}{2} - 	ext{Number of nonbonding electrons}$$

Question 4

A nitrogen atom in ammonia ($$\mathrm{NH_3$}) $$has how many valence electrons assigned to it when calculating formal charge?

Accepted Answer

$$5$$

Question 5

Which statement about resonance structures is TRUE?

Accepted Answer

The resonance hybrid is more stable than any individual resonance form.

Question 6

In the acetate ion ($$\mathrm{CH_3CO_2^-}$$), which electrons are most likely to move when drawing resonance structures?

Accepted Answer

Electrons in lone pairs or $$\pi$$ bonds

Question 7

Why does benzene have equivalent carbon–carbon bonds?

Accepted Answer

Because it is a resonance hybrid of two forms

Question 8

Which rule about resonance forms is violated if a resonance structure shows a carbon atom with 10 electrons?

Accepted Answer

Resonance forms obey normal rules of valency

Question 9

Which of the following is NOT a valid movement in resonance structures?

Accepted Answer

Movement of atoms

Question 10

What is the formal charge on sulfur in dimethyl sulfoxide ($$\mathrm{(CH_3$)_2SO}$$)?

Accepted Answer

$$+1$$

Question 11

Which of the following molecules does NOT have a dipole moment?

Accepted Answer

Methane ($$\mathrm{CH_4$})$$

Question 12

Which of the following statements about resonance in the carbonate ion ($$\mathrm{CO_3$^{2-}}) is $$correct?

Accepted Answer

The true structure is a hybrid of three resonance forms.

Question 13

Which of the following is a consequence of resonance stabilization in organic molecules?

Accepted Answer

Bond lengths are intermediate between single and double bonds.

Question 14

In the resonance forms of acetone anion, what does the curved arrow represent?

Accepted Answer

Movement of electrons

Question 15

Which of the following is TRUE regarding the resonance forms of 2,4-pentanedione?

Accepted Answer

The resonance hybrid is more stable than any individual resonance form.

Question 16

Which atom in the following list is most likely to have a formal charge of $$-1 in a $$common organic molecule?

Accepted Answer

Oxygen

Question 17

Which of the following is a valid resonance structure for the acetate ion ($$\mathrm{CH_3CO_2^-}$$)?

Accepted Answer

A structure with a double bond to one oxygen and a single bond to the other, with a negative charge on the singly bonded oxygen.

Question 18

Which of the following statements about formal charge is correct?

Accepted Answer

Formal charge helps identify the most stable resonance structure.

Question 19

Which molecule below is best described as a resonance hybrid rather than a single Lewis structure?

Accepted Answer

Benzene ($$\mathrm{C_6H_6})$$

Polar Covalent Bonds, Formal Charges, and Resonance in Organic Molecules

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