Atoms and the Periodic Table

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Atom Noun

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[at-um]

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Atom

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The basic building block of all matter, consisting of a nucleus of protons and neutrons orbited by electrons.

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

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Proton Noun

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[pro-ton]

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Proton

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A stable subatomic particle with a positive electric charge, found in the nucleus of every atom.

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Example: This diagram shows that protons are particles found inside the central nucleus of an atom, along with neutrons.

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Neutron Noun

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[noo-tron]

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Neutron

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A subatomic particle of about the same mass as a proton but without an electric charge, present in all atomic nuclei except those of ordinary hydrogen.

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Example: This diagram shows a neutron (blue sphere) as a particle located inside the atom's central nucleus, along with protons (green spheres) and orbiting electrons (red spheres).

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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 all atoms and acting as the primary carrier of electricity in solids.

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Example: This diagram shows electrons (blue dots) as particles that orbit the nucleus of an atom in specific energy shells or layers.

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Nucleus Noun

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[noo-klee-uhs]

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Nucleus

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The positively charged central core of an atom, consisting of protons and neutrons and containing nearly all its mass.

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Example: This diagram shows the nucleus, containing protons and neutrons, at the center of an atom with electrons orbiting it.

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Atomic Mass Noun

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[uh-tom-ik mas]

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Atomic Mass

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The mass of an atom, expressed in atomic mass units, which is approximately the sum of the protons and neutrons.

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Example: This diagram of a periodic table element tile for Carbon shows that the number at the bottom, 12.01, is the average atomic mass.

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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 only of atoms that all have the same numbers of protons in their atomic nuclei.

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Example: This diagram shows how an element, like Carbon, is displayed on the periodic table with its atomic number, symbol, name, and atomic mass.

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Periodic Table Noun

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[peer-ee-od-ik tey-buhl]

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Periodic Table

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A tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties.

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Example: This chart, the Periodic Table, organizes all known chemical elements by their atomic number, with a key explaining the data shown for each element.

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Period Noun

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[peer-ee-uhd]

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Period

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A horizontal row in the periodic table, where elements within the same period have the same number of electron shells.

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Example: This diagram shows that a 'period' in the periodic table is a row containing a specific set of elements, using Period 3 as an example.

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Group Noun

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[groop]

Back

Group

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A vertical column in the periodic table containing elements with similar chemical behaviors due to having the same number of valence electrons.

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Example: The periodic table is organized into vertical columns called Groups. Elements in the same group, like the Alkali Metals (purple), share similar chemical properties.