Covalent bonds form by overlap of half-filled atomic orbitals sharing a pair of electrons.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
Valence bond theory describes covalent bonding as the overlap of half-filled atomic orbitals on two atoms, with the two electrons paired in opposite spins in the overlap region. The greater the overlap, the stronger the bond, which explains why bonds involving different orbitals vary in strength. The theory accounts for the directionality of bonds because orbitals overlap along specific directions. It describes bonding in a localized way, with each bond a separate pair of electrons between two atoms. For polyatomic molecules with specific geometries it must be supplemented by hybridization.
Key ideas: Rules: bonds need overlap of orbitals each holding one electron with opposing spin, and strength rises with overlap. Count unpaired electrons to predict valency: oxygen has two half-filled 2p orbitals so forms two bonds. Hybridization is added to get the observed angles. Localized pair bonds are drawn as sigma or pi types.
Common mistakes and connections: VB theory struggles to explain the paramagnetism of O2, odd-electron bonds and the colour of many species, and students wrongly claim the theory predicts them. Another common error is thinking overlap means orbitals physically merge as hard objects. Contrasts with MO theory, and links to hybridization and sigma and pi bonds.
Bonding arises from overlap of half-filled orbitals, such as two hydrogen 1s orbitals, which places electron density between the two nuclei. The interactive lesson shows this as a live animation or chart.
The H-H bond in H2 forms from the overlap of two half-filled 1s orbitals.
Covalent bonds form by overlap of half-filled atomic orbitals sharing a pair of electrons.
Valence Bond Theory is a intermediate topic in Bonding & Molecular Structure. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Bonding & Molecular Structure first: Square Planar Geometry, Square Pyramidal Geometry, Bond Angle Deviations.
The next topics in Bonding & Molecular Structure are Sigma Bond and Pi Bond.
Yes. The interactive lesson includes a self-check question on Valence Bond Theory, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Valence Bond Theory is topic 50 of 104 in Bonding & Molecular Structure.