Lewis Structures and Molecular Geometry

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Molecular Geometry Noun

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

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Molecular Geometry

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The specific three-dimensional arrangement of atoms in a molecule, which is defined by the positions of the atomic nuclei.

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Example: This image shows how atoms in a water molecule (H₂O) are arranged in a specific 'bent' shape, which is an example of molecular geometry.

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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 theory stating that electron pairs in an atom's outer shell repel each other, determining the molecule's overall shape.

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Example: This image shows how VSEPR theory predicts molecular shapes; water (H₂O) has a bent shape, while carbon dioxide (CO₂) is a straight line.

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Lewis Structure Noun

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[loo-is struhk-cher]

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Lewis Structure

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A diagram showing the bonding between atoms and any lone pairs of electrons that exist within a molecule.

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Example: This image shows that a Lewis Structure is a special diagram of a molecule that includes all valence electrons, both shared pairs and unshared lone pairs.

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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 two adjacent bonds that originate from the same central atom in a molecule's structure.

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Example: This diagram uses a simple molecule to show that a bond angle is the angle formed between two chemical bonds that are attached to the same central atom.

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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 that are shared between two atoms, forming a covalent bond that holds the atoms together.

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Example: This diagram shows a pair of electrons (blue dots) shared between a nitrogen and a hydrogen atom, forming a chemical bond called a bonding pair.

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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 are not shared with another atom in a covalent bond; also called a nonbonded pair.

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Example: This image shows a water molecule. The two pairs of dots on the central oxygen atom, shown as lobes, are not involved in bonding and are called lone pairs.

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Central Atom Noun

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[sen-truhl at-uhm]

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Central Atom

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The specific atom in a molecule to which all other atoms are directly bonded in the molecular structure.

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Example: This diagram shows a water molecule where the single oxygen atom is bonded to two hydrogen atoms, making the oxygen the central atom.

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Valence Electron Noun

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[vey-luhns ih-lek-tron]

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Valence Electron

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An electron located in the outermost energy level of an atom that is available to participate in chemical bonding.

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Example: This Bohr model of a sodium atom shows electrons in shells; the single electron in the outermost shell is the valence electron.

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Linear Geometry Noun

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[lin-ee-er jee-om-i-tree]

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Linear Geometry

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A molecular shape where atoms are arranged in a straight line, resulting in a bond angle of exactly 180 degrees.

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Example: This image shows a linear graph for converting temperature, which is unrelated to the linear geometry of molecules where atoms are arranged in a straight line.

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Trigonal Planar Noun

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[trig-uh-nl pley-ner]

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Trigonal Planar

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A molecular shape with one central atom and three surrounding atoms in the same plane, creating 120 degree bond angles.

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Example: This diagram shows a central atom bonded to three other atoms, all lying flat on a single plane with 120-degree angles between them.