Flashcards: Chemistry Final Semester A 2025

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Atom

Back

The smallest unit of an element that maintains the identity of the element

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Element

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A pure substance that cannot be broken down into anything simpler or more stable

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Compound

Back

A pure substance that can be chemically broken down into simple and more stable substances; when atoms of two or more elements are chemically combined

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Law of conservation of matter

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Matter is never created or destroyed, it only changes forms

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Valence electrons

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Electrons in the outermost energy level of the electron cloud

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Atomic number

Back

Number of protons in an atom of the element; used to identify an element

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Mass number

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Number of protons and neutrons in the nucleus of an atom

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Isotopes

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Atoms of the same element with different numbers of neutrons

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Average atomic mass

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Weighted average of all of the different versions of an element; measured in amu

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Radioactive decay

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When matter and energy are spontaneously emitted from an unstable nucleus that can no longer hold itself together