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

$$\text{Formal charge} = \text{number of valence electrons normally} - (\text{number of non-bonded electrons} + \frac{1}{2} \times \text{number of bonded electrons})$$

Question 1

Which of the following statements best describes a sigma ($$\sigma) $$bond?

Accepted Answer

It is the first bond formed between two atoms and results from head-on overlap of orbitals.

Question 2

In the molecule ethene ($$\mathrm{C_2H_4}$$), how many sigma ($$\sigma) $$and pi ($$\pi) $$bonds are present?

Accepted Answer

$$5\ \sigma$$ and $$1\ \pi$$

Question 3

Which of the following best explains why pi ($$\pi) $$bonds restrict rotation around the bond axis?

Accepted Answer

Pi bonds have electron density above and below the bond axis, so rotation would break the overlap.

Question 4

What is the bond order of the carbon-nitrogen bond in the cyanide ion ($$\mathrm{CN^-}$$)?

Accepted Answer

$$3$$

Question 5

Which of the following statements about resonance structures is correct?

Accepted Answer

The actual structure is a hybrid or average of all resonance forms.

Question 6

Given the nitrate ion ($$\mathrm{NO_3$^-}$$), what is the bond order of the N–O bonds?

Accepted Answer

$$1.33$$

Question 7

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

Accepted Answer

$$	ext{Formal charge} = 	ext{number of valence electrons normally} - (	ext{number of non-bonded electrons} + \frac{1}{2} 	imes 	ext{number of bonded electrons})$$

Question 8

Which structure for $$\mathrm{CCl_2O} is $$most dominant based on formal charges?

Accepted Answer

The structure where the formal charges are closest to zero on all atoms.

Question 9

What is the hybridization of the central carbon atom in ethyne ($$\mathrm{C_2H_2}$$)?

Accepted Answer

$$sp$$

Question 10

How many electron domains are associated with $$sp^2$$ hybridization?

Accepted Answer

3

Question 11

Which of the following statements about hybridization is correct?

Accepted Answer

Hybridization allows for the formation of equivalent energy orbitals for bonding.

Question 12

In the molecule shown below (propyne, $$\mathrm{CH_3C \equiv CH}$$), what is the hybridization of the central carbon atom?

Accepted Answer

$$sp$$

Question 13

Which of the following best describes the relationship between bond order, bond length, and bond energy?

Accepted Answer

As bond order increases, bond length decreases, and bond energy increases.

Question 14

Which of the following is true about the rotation around single, double, and triple bonds?

Accepted Answer

Free rotation is possible around single bonds only.

Question 15

A molecule has 4 electron domains around its central atom. What is the expected hybridization?

Accepted Answer

$$sp^3$$

Question 16

Which of the following is a consequence of delocalized electrons in resonance structures?

Accepted Answer

Bond lengths are intermediate between single and double bonds.

Question 17

In the acetate ion ($$\mathrm{CH_3CO_2^-}$$), what is the bond order of the two C–O bonds?

Accepted Answer

$$1.5$$

Question 18

Which of the following is NOT a characteristic of a sigma ($$\sigma) $$bond?

Accepted Answer

It is formed by side-to-side overlap of p orbitals.

Question 19

Which atom should carry a negative formal charge if it cannot be avoided, according to formal charge rules?

Accepted Answer

The most electronegative atom.

Question 20

Which of the following best describes the hybridization of the central atom in methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

$$sp^3$$

Sigma and Pi Bonds, Bond Order, Formal Charge, and Hybridization: Core Concepts in Organic Chemistry

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