Chemical Formulas

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Chemical Formula Noun

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[kem-i-kuhl for-myoo-luh]

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Chemical Formula

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A shorthand expression using chemical symbols and numbers to represent the elements in a compound and their relative proportions.

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Example: A chemical formula, like C₆H₁₂O₆ for glucose, uses element symbols and numbers to show the exact number of atoms of each element in one molecule.

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Atom Noun

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[at-uhm]

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Atom

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The basic unit of a chemical element that is rearranged during chemical reactions to form new compounds.

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Example: This diagram shows the structure of an atom, with a central nucleus containing protons and neutrons, and electrons orbiting the nucleus in shells.

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Ion Noun

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[ahy-on]

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Ion

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An atom or molecule that possesses a net electric charge due to the loss or gain of one or more electrons.

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Example: A neutral sodium atom with 11 protons and 11 electrons loses one electron, becoming a positive sodium ion (Na¹⁺) with an overall +1 charge.

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Element Noun

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[el-uh-muhnt]

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Element

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A pure substance consisting of only one type of atom, which is designated by a specific chemical symbol.

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Example: This diagram shows a Bohr model of a Sodium atom, a specific example of an element. An element is a pure substance made of one atom type.

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Molecule Noun

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[mol-i-kyool]

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Molecule

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A group of two or more atoms held together by chemical bonds, representing the smallest unit of a chemical compound.

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Example: This image shows a water molecule, made of two hydrogen (H) atoms and one oxygen (O) atom, representing the chemical formula H₂O.

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Compound Noun

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[kom-pound]

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Compound

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A substance formed when two or more different chemical elements are chemically bonded together in a fixed ratio.

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Example: This diagram shows a molecule of carbon dioxide (CO₂), a compound made of one carbon atom chemically bonded to two oxygen atoms.

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Qualitative Information Noun

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[kwol-i-tey-tiv in-fer-mey-shuhn]

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Qualitative Information

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Information within a chemical formula that identifies the types of atoms or ions present in a given substance.

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Example: This diagram shows the types of particles (blue, orange, green) in a mixture, which is qualitative information because it describes 'what' is present, not 'how much'.

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Quantitative Information Noun

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[kwon-ti-tey-tiv in-fer-mey-shuhn]

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Quantitative Information

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Information within a chemical formula that specifies the exact number of each type of atom or ion present.

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Example: The numbers in the chemical equation (2H₂, O₂, 2H₂O) represent specific, countable quantities of molecules involved in the reaction.

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Chemical Symbol Noun

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[kem-i-kuhl sim-buhl]

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Chemical Symbol

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A one- or two-letter abbreviation for a chemical element, used in formulas with the first letter always capitalized.

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Example: This image shows the periodic table information for Helium. The large letters 'He' in the center are the chemical symbol, a one or two-letter abbreviation for an element.

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Subscript Noun

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[suhb-skript]

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Subscript

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A number written in the lower right corner after a chemical symbol to indicate the number of atoms of that element.

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Example: The chemical formula for water, H₂O, has a subscript '2' because a single water molecule contains two atoms of hydrogen (H).