VSEPR

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VSEPR Theory Noun

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[ves-per thee-uh-ree]

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VSEPR Theory

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A model used to predict the 3D geometry of molecules by minimizing the electrostatic repulsion between valence electron pairs.

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Example: VSEPR theory explains molecule shapes. Electron pairs repel each other, creating specific angles, like the bent shape of water (H₂O) and the linear shape of carbon dioxide (CO₂).

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Molecular Geometry Noun

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[muh-lek-yuh-ler jee-om-i-tree]

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Molecular Geometry

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The three-dimensional arrangement of atoms within a molecule, which is a key factor in determining its chemical properties.

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Example: This image shows a methane molecule (CH4), where the atoms arrange themselves into a specific 3D shape (tetrahedral) to be as far apart as possible.

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Electron Region Noun

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[i-lek-tron ree-juhn]

Back

Electron Region

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An area around a central atom where electrons are concentrated, which can be a lone pair or a chemical bond.

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Example: This image shows a simplified Bohr model of a water molecule, with electrons orbiting the atomic nuclei in fixed, circular paths or shells.

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Steric Number Noun

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[ster-ik nuhm-ber]

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Steric Number

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The total count of electron regions around a central atom, calculated by summing the number of bonded atoms and lone pairs.

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Example: The Steric Number of a central atom is calculated by adding the number of atoms bonded to it and the number of lone pairs it has.

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Lone Pair Noun

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[lohn pair]

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Lone Pair

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A pair of valence electrons that is not involved in bonding and belongs exclusively to a single atom.

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Example: This diagram shows an ammonia molecule (NH3). The large blue cloud labeled 'Lone pair' is a pair of electrons on the nitrogen atom not used for bonding, which pushes the hydrogen atoms down.

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Bonding Pair Noun

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[bon-ding pair]

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Bonding Pair

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A pair of electrons shared between two atoms, forming a covalent bond that holds the atoms together in a molecule.

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Example: This diagram shows that a bonding pair is a pair of electrons shared between two atoms, like the ones connecting the central Nitrogen (N) and a Hydrogen (H) atom.

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Bond Angle Noun

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[bond ang-guhl]

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Bond Angle

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The angle formed between three atoms across at least two bonds, which is a defining feature of molecular geometry.

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Example: This diagram shows the angle formed between three connected atoms in a molecule, which is called the bond angle.

Front

Molecular Polarity Noun

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[muh-lek-yuh-ler poh-lar-i-tee]

Back

Molecular Polarity

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The overall distribution of electrical charge within a molecule, resulting from its bond polarities and three-dimensional shape.

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Example: This diagram of a water molecule shows how the oxygen atom pulls electrons more strongly, creating a partial negative charge (δ-), while the hydrogen atoms become partially positive (δ+). This uneven charge distribution makes the molecule polar.

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Hybridization Noun

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[hy-brid-ih-zay-shun]

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Hybridization

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The concept of mixing atomic orbitals to form new, equivalent hybrid orbitals suitable for forming stable chemical bonds.

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Example: This diagram shows how a central carbon atom's orbitals change shape to bond with four hydrogen atoms, forming a molecule of methane with a specific 3D structure.

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Sigma (σ) bond Noun

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[sig-muh bond]

Back

Sigma (σ) bond

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The strongest type of covalent bond, formed by the direct, head-on overlap of atomic orbitals along the internuclear axis.

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Example: This diagram shows how a sigma (σ) bond forms when atomic orbitals, like s-orbitals (spheres) and p-orbitals (dumbbells), overlap directly end-to-end.