$\text{Formal charge} = \text{Valence electrons} - (\text{Lone pair electrons} + \frac{1}{2} \text{Bonding electrons})$

Question 1

Which of the following molecules is an example of a species that violates the octet rule due to hypervalence?

Accepted Answer

SO$_4^{2-}$ (sulfate ion)

Question 2

What is the total number of valence electrons in the Lewis structure of the nitrate ion, NO$_3^-$?

Accepted Answer

$24$

Question 3

Which step comes FIRST when drawing a Lewis structure for a molecule?

Accepted Answer

Count the total number of valence electrons.

Question 4

In the Lewis structure for ammonia (NH$_3$), does nitrogen obey the octet rule?

Accepted Answer

Yes, because it has 8 electrons around it.

Question 5

Which of the following is the correct formula for calculating the formal charge on an atom in a Lewis structure?

Accepted Answer

$	ext{Formal charge} = 	ext{Valence electrons} - (	ext{Lone pair electrons} + \frac{1}{2} 	ext{Bonding electrons})$

Question 6

Which molecule below is most likely to have resonance structures?

Accepted Answer

O$_3$

Question 7

Which of the following is a common exception to the octet rule?

Accepted Answer

Hydrogen requires only two electrons (a duet).

Question 8

What is the hybridization of the central carbon atom in CH$_4$?

Accepted Answer

$sp^3$

Question 9

Which statement best explains why ethylene (C$_2$H$_4$) is planar?

Accepted Answer

The double bond between the carbons restricts rotation, keeping all atoms in the same plane.

Question 10

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

Accepted Answer

A bond formed by the end-to-end overlap of orbitals along the internuclear axis.

Question 11

How many lone pairs are present on the central atom in the Lewis structure of NF$_3$?

Accepted Answer

1

Question 12

Which of the following molecules contains a central atom with an incomplete octet?

Accepted Answer

BF$_3$

Question 13

What is the formal charge on the nitrogen atom in the ammonium ion (NH$_4^+$)?

Accepted Answer

$0$

Question 14

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

Accepted Answer

A bond formed by the side-to-side overlap of p orbitals above and below the internuclear axis.

Question 15

Which molecule below is most likely to have an expanded octet?

Accepted Answer

SF$_6$

Question 16

In the Lewis structure of CO$_2$, what is the bond order between the carbon and each oxygen atom?

Accepted Answer

$2$

Question 17

Which of the following is a correct statement about resonance structures?

Accepted Answer

Resonance structures are different possible arrangements of electrons in the same molecule.

Question 18

Which of the following molecules is polar due to its molecular geometry?

Accepted Answer

CH$_3$Cl

Question 19

Which of the following statements about hybridization is correct?

Accepted Answer

sp$^2$ hybridization results in a trigonal planar geometry.

Question 20

Which of the following molecules contains both sigma ($\sigma$) and pi ($\pi$) bonds?

Accepted Answer

C$_2$H$_4$

Molecular Structure & Bonding: Lewis Structures, Formal Charge, and Valence Bond Theory

Study Guide - Practice Questions