Q: What is the correct formula for calculating bond order using MO theory?

$\dfrac{\text{number of bonding electrons} - \text{number of antibonding electrons}}{2}$

Question 1

According to Valence Bond (VB) theory, what is the primary requirement for a covalent bond to form between two atoms?

Accepted Answer

The atomic orbitals must overlap and a pair of electrons must occupy the overlap region.

Question 2

Which statement best describes the electron density in a sigma ($\sigma$) bond?

Accepted Answer

Electron density is greatest along the axis directly between the two nuclei.

Question 3

Which of the following is NOT a central theme of Valence Bond theory?

Accepted Answer

Delocalization of electrons over the entire molecule

Question 4

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 5

Which type of atomic orbital overlap leads to the formation of a pi ($\pi$) bond?

Accepted Answer

Side-to-side overlap of unhybridized p orbitals

Question 6

What is the hybridization of the central atom in $\mathrm{BF_3}$?

Accepted Answer

$sp^2$

Question 7

How many hybrid orbitals are formed when one s orbital and two p orbitals are mixed?

Accepted Answer

Three

Question 8

Which molecular geometry is associated with $sp^3d$ hybridization?

Accepted Answer

Trigonal bipyramidal

Question 9

According to Molecular Orbital (MO) theory, what is the bond order of $\mathrm{O_2}$ given the following electron configuration: $\sigma_{2s}^2,\ \sigma_{2s}^{*2},\ \sigma_{2p}^2,\ \pi_{2p}^4,\ \pi_{2p}^{*2}$?

Accepted Answer

2

Question 10

Which property of $\mathrm{O_2}$ is correctly predicted by MO theory but not by VB theory?

Accepted Answer

Its paramagnetism

Question 11

What is the correct formula for calculating bond order using MO theory?

Accepted Answer

$\dfrac{	ext{number of bonding electrons} - 	ext{number of antibonding electrons}}{2}$

Question 12

Which statement about bonding and antibonding molecular orbitals is TRUE?

Accepted Answer

Bonding molecular orbitals are lower in energy and have electron density between the nuclei.

Question 13

Which molecule is expected to be diamagnetic based on its MO electron configuration?

Accepted Answer

$\mathrm{N_2}$

Question 14

What is the bond order of $\mathrm{He_2}$ according to MO theory?

Accepted Answer

0

Question 15

Which of the following statements about hybrid orbitals is FALSE?

Accepted Answer

Hybrid orbitals exist in isolated atoms.

Question 16

Which of the following molecules can exhibit cis/trans isomerism?

Accepted Answer

$\mathrm{CHCl=CHBr}$

Question 17

Why is benzene ($\mathrm{C_6H_6}$) unusually stable compared to typical alkenes?

Accepted Answer

Its electrons are delocalized over the entire ring, lowering its energy.

Question 18

Which hybridization is associated with a linear electron-pair geometry?

Accepted Answer

$sp$

Question 19

A molecule has four regions of high electron density around its central atom. What is the expected hybridization?

Accepted Answer

$sp^3$

Question 20

Which of the following best explains why rotation is restricted around a double bond?

Accepted Answer

The pi ($\pi$) bond, formed by side-to-side overlap, locks the atoms in place.

Valence Bond Theory and Sigma/Pi Bonding: Structured Study Notes

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