Modeling Atoms

Front

Atom Noun

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[at-uhm]

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Atom

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The smallest particle of an element that retains its identity in a chemical reaction and is composed of subatomic particles.

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

Front

Subatomic Particle Noun

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

Back

Subatomic Particle

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The smaller constituent particles of an atom, which include protons, neutrons, and electrons, each with unique properties and locations.

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

Front

Proton Noun

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[pro-ton]

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Proton

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A positively charged subatomic particle located in the atom's nucleus, with a mass of approximately one atomic mass unit.

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Example: This diagram shows that a proton is a positively charged particle (+) found clustered with neutrons in the central nucleus of an atom.

Front

Neutron Noun

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[noo-tron]

Back

Neutron

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A subatomic particle with no electrical charge, found in the atom's nucleus, with a mass of about one amu.

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Example: This diagram shows a neutron as a particle located inside the atom's central nucleus, alongside protons, while electrons orbit the nucleus.

Front

Electron Noun

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[uh-lek-tron]

Back

Electron

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A negatively charged subatomic particle found in the electron cloud surrounding the nucleus, with a very small, negligible mass.

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Example: This model of an atom shows electrons as particles that orbit the central nucleus in specific paths called shells.

Front

Nucleus Noun

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[noo-klee-uhs]

Back

Nucleus

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The dense, positively charged central core of an atom, composed of protons and neutrons, containing most of the atom's mass.

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Example: This diagram models a helium atom, showing the nucleus at the center, which contains positively charged protons and neutral neutrons.

Front

Electron Cloud Noun

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[uh-lek-tron kloud]

Back

Electron Cloud

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The region surrounding an atom's nucleus where electrons are located, accounting for most of the atom's volume but little mass.

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Example: This diagram shows an atom's central nucleus and the surrounding electron cloud, which is the region where electrons are most likely to be found.

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Element Noun

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[el-uh-muhnt]

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Element

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The simplest form of matter with a unique set of properties, defined by the number of protons in its atoms.

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Example: This Bohr model shows a single atom of the element Sodium (Na), which has electrons arranged in specific energy shells (2, 8, 1).

Front

Atomic Number Noun

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[uh-tom-ik nuhm-ber]

Back

Atomic Number

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The number of protons in the nucleus of an atom, which uniquely identifies an element and equals the electron count.

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Example: This periodic table key shows that the atomic number, located at the top of the element's box, is equal to the number of protons in an atom's nucleus.

Front

Mass Number Noun

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[mas nuhm-ber]

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Mass Number

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The total number of protons and neutrons in an atom's nucleus, representing the approximate mass of that specific atom.

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Example: This diagram shows the standard notation for an element, where the mass number (total protons and neutrons) is the top number next to the element's symbol.