2.11: Key Terms

Foundations of General, Organic, and Biological Chemistry: An Integrated Approach · LibreTexts

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    From LibreTexts, under CC BY-NC-SA 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

    • Atom: The smallest unit of an element that retains its chemical properties.
    • Diatomic molecule: A molecule consisting of two atoms, often of the same element (e.g., O₂, H₂).
    • Subatomic particles: Particles that make up atoms: protons, neutrons, and electrons.
    • Nucleus: The dense central part of an atom containing protons and neutrons.
    • Protons: Positively charged subatomic particles found in the nucleus.
    • Neutrons: Neutral subatomic particles found in the nucleus.
    • Electrons: Negatively charged subatomic particles found outside the nucleus.
    • Isotopes: Atoms of the same element with different numbers of neutrons.
    • Atomic number (Z): The number of protons in the nucleus of an atom.
    • Mass number (A): The total number of protons and neutrons in an atom.
    • Chemical symbol: A one- or two-letter abbreviation for an element (e.g., H for hydrogen).
    • Ion: An atom or molecule with a net electric charge due to the loss or gain of electrons.
    • Anion: A negatively charged ion.
    • Cation: A positively charged ion.
    • Atomic mass unit (amu): A unit of mass equal to one-twelfth the mass of a carbon-12 atom.
    • Weighted average: An average that takes into account the relative abundances of isotopes.
    • Atomic mass: The weighted average mass of an element's atoms based on isotopic abundance.
    • Periodic table: A chart organizing elements by increasing atomic number and similar properties.
    • Groups: Vertical columns in the periodic table; elements in a group have similar properties.
    • Alkali metals: Group 1 elements, highly reactive, especially with water.
    • Alkaline earth metals: Group 2 elements, reactive metals but less so than alkali metals.
    • Halogens: Group 17 elements, very reactive nonmetals.
    • Noble gases: Group 18 elements, inert gases with full outer electron shells.
    • Period: A horizontal row in the periodic table.
    • Metal: An element that is typically shiny, conductive, malleable, and ductile.
    • Non-metal: An element that lacks metallic properties; usually poor conductors.
    • Metalloid: An element with properties intermediate between metals and non-metals.
    • Semimetals: Another term for metalloids.
    • Main group elements: Elements in groups 1, 2, and 13–18 of the periodic table.
    • Transition metals: Elements in groups 3–12, known for forming colorful compounds and variable oxidation states.
    • Inner transition metals: Elements in the lanthanide and actinide series.
    • Lanthanides: The 14 elements following lanthanum (atomic numbers 58–71).
    • Actinides: The 14 elements following actinium (atomic numbers 90–103).
    • Quantum number: A number that describes the energy level and properties of an electron.
    • Quantized: Existing only in specific, discrete values.
    • Quantum mechanics: The branch of physics that describes the behavior of very small particles.
    • Shells: Energy levels where electrons reside around the nucleus.
    • Subshells: Divisions within electron shells (s, p, d, f).
    • Orbitals: Regions in an atom where there is a high probability of finding electrons.
    • Spin: A quantum property of electrons; can be +½ or −½.
    • Electron configuration: The arrangement of electrons in an atom’s orbitals.
    • Aufbau Principle: Electrons fill orbitals starting with the lowest energy levels first.
    • Hund's Rule: Electrons occupy separate orbitals in the same subshell before pairing up.
    • Pauli Exclusion Principle: No two electrons in the same atom can have the same set of quantum numbers.
    • Valence electrons: Electrons in the outermost shell that determine chemical reactivity.
    • Core electrons: Electrons in inner shells that are not involved in bonding.
    • Noble gas configuration: A shorthand for electron configuration using the nearest noble gas.
    • Orbital diagram: A visual representation of electron arrangement using arrows in boxes.
    • Atomic radius: The distance from the nucleus to the outermost electron of an atom.

    This page titled 2.11: Key Terms was last modified on Wed, 30 Jul 2025 19:32:50 GMT and is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Burçak Artun, Gorkem Ermut, and Semere Bairu.