Valence Bond Theory Overview

What is the primary factor that determines the strength of a covalent bond according to Valence Bond Theory?

What type of bond is formed when electron density is located along the internuclear axis?

What is the electron configuration of a hydrogen atom?

How does the potential energy of the system of two hydrogen atoms change as they approach each other to form a bond?

What is the reason for the increase in potential energy at very short internuclear distances during bond formation in H₂?

What happens to the energy of the system when the H₂ bond forms?

What is the relationship between the internuclear distance at minimum potential energy and the bond length?

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

Valence Bond Theory

Valence bond theory describes covalent bonds as the overlap of atomic orbitals
When a covalent bond forms, there is shared electron density between the nuclei of the bonded atoms.
This shared density holds the atoms together.
In valence bond theory, the shared electron density occurs when a valence orbital from one atom overlaps with a valence orbital from another atom.
Two electrons with opposite spins are shared in the overlap region, forming the covalent bond.
The greater the orbital overlap, the stronger the bond.

Sigma (σ) Bonds

A sigma (σ) bond is formed when electron density is along the internuclear axis
Single bonds are always sigma bonds
The formation of σ bonds can be seen in the formation of H₂, HCl, and Cl₂

Bond Formation in H₂

Hydrogen's electron configuration is 1s¹.
Each hydrogen atom has an unpaired electron in its valence 1s orbital.
As the two hydrogen atoms get closer, their 1s orbitals begin to overlap.
Electron density builds up in the overlap region where the two valence electrons with opposite spins are shared, forming a sigma bond.

Factors Affecting Bond Strength

Overlap: The extent of orbital overlap determines the strength of the bond. The greater the overlap, the stronger the bond
Internuclear Distance: As atoms get closer, the electron-nuclear attraction increases, while the electron-electron repulsion starts to increase. The distance at the minimum potential energy corresponds to the observed bond length.
Bond Energy: The energy released when a bond forms (exothermic) is equal to the bond energy (or bond enthalpy). Energy must be input (endothermic) to break the formed bond.

This quiz explores the key concepts of valence bond theory, including the formation of covalent bonds through orbital overlaps. It covers the specifics of sigma bonds and the bond formation in hydrogen molecules. Test your understanding of how atomic orbitals interact to create chemical bonds.