Isotopes and Ions

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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 of only one type of atom, distinguished by its unique atomic number.

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Example: This diagram shows a single atom of the element Sodium, with its nucleus (Na) and electrons arranged in shells (2, 8, 1).

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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 the chemical properties of that element.

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Example: An atom consists of a central nucleus (containing protons and neutrons) surrounded by electrons orbiting in shells. The number of each particle determines the atom's properties.

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Proton Noun

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[proh-ton]

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Proton

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A stable, positively charged subatomic particle found in the nucleus of an atom that determines the atomic number.

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Example: This diagram shows a proton, the positively charged particle, at the center of a simple hydrogen atom, which also has one orbiting electron.

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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 electrical charge, located in the nucleus of an atom alongside protons.

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Example: This diagram shows a neutron as a neutral particle found inside the atom's central nucleus, alongside protons, with electrons orbiting outside.

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Electron Noun

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[ih-lek-tron]

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Electron

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A stable, negatively charged subatomic particle that occupies orbitals surrounding the atom's nucleus.

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Example: This diagram shows a negatively charged electron orbiting the central nucleus of an atom, which contains positively charged protons and neutral neutrons.

Front

Nucleus Noun

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[noo-klee-uhs]

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Nucleus

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The dense, positively charged central region of an atom, composed of protons and neutrons.

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Example: The nucleus is the central part of an atom, containing positively charged protons and neutral neutrons, as shown in this Lithium atom model.

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Atomic Number Noun

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[uh-tom-ik nuhm-ber]

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Atomic Number

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The number of protons in an atom's nucleus, which uniquely identifies a chemical element.

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Example: This diagram of an oxygen atom shows the nucleus contains 8 protons, which defines its atomic number as 8.

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Isotope Noun

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[ahy-suh-tohp]

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Isotope

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Atoms of the same element having the same number of protons but different numbers of neutrons.

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Example: This diagram shows that isotopes of an element, like carbon, have the same number of protons but a different number of neutrons in their nucleus.

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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 found in the nucleus of a specific atom or isotope.

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Example: This diagram shows that the mass number (27) is the total count of protons (13) and neutrons (14) in an atom's nucleus.

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Radioactive Isotope Noun

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[rey-dee-oh-ak-tiv ahy-suh-tohp]

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Radioactive Isotope

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An unstable isotope of an element that decays spontaneously, emitting radiation as its nucleus changes.

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Example: This graph shows that after each half-life passes, the amount of a radioactive isotope decreases by half, demonstrating the process of radioactive decay.