Atoms and Atomic Structure

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Atom Noun

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[at-uhm]

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Atom

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The fundamental particle of a chemical element, representing the smallest unit of matter that retains the element's properties.

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

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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 whose atoms all have the same number of protons and cannot be broken down by chemical means.

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Example: This diagram shows the atomic structure of a single element, Sodium (Na), illustrating that an element is a pure substance made of only one type of atom.

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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 image shows a molecule of carbon dioxide (CO₂), a compound formed when one carbon atom chemically bonds with two oxygen atoms.

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Subatomic Particle Noun

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[suhb-uh-tom-ik par-ti-kuhl]

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Subatomic Particle

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A particle smaller than an atom, such as a proton, neutron, or electron, that is a constituent of atoms.

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Example: This diagram shows an atom's three main subatomic particles: protons and neutrons clustered in the central nucleus, and electrons orbiting in outer shells.

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Electron Noun

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[ih-lek-tron]

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Electron

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A stable subatomic particle with a negative electric charge, found in orbitals surrounding the nucleus of an atom.

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Example: This diagram shows an electron, a negatively charged particle, as it orbits the nucleus of a nitrogen atom in the Bohr atomic model.

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Proton Noun

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[proh-ton]

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Proton

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A stable subatomic particle with a positive electric charge, located within the atomic nucleus of an atom.

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Example: This diagram shows a proton as a particle located inside the central nucleus of an atom, along with neutrons and orbiting electrons.

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Neutron Noun

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[noo-tron]

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Neutron

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A subatomic particle with no electric charge and a mass similar to a proton, found in the atomic nucleus.

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Example: This diagram shows a neutron (blue), a particle with no charge, located inside the atom's central nucleus alongside a positively charged proton.

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Nucleus Noun

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[noo-klee-uhs]

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Nucleus

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The small, dense, positively charged center of an atom, which is composed of protons and neutrons.

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Example: An atom's nucleus is the dense central core, containing positively charged protons and neutral neutrons, with negatively charged electrons orbiting around it.

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Cathode Ray Noun

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[kath-ohd rey]

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Cathode Ray

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A beam of electrons that originates from the negatively charged electrode, or cathode, within a vacuum tube.

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Example: This diagram shows a cathode ray, a beam of particles, bending toward a positive plate, proving the particles in the ray are negatively charged.

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Orbital Noun

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[awr-bi-tl]

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Orbital

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A region of space around an atom's nucleus where there is a high probability of finding an electron.

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Example: This image shows the three different p-orbitals (px, py, pz), which are dumbbell-shaped regions around an atom's nucleus where an electron is likely to be found.