Isotopes and Average Atomic Mass

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Proton Noun

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[pro-ton]

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Proton

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A subatomic particle with a positive electric charge found within the nucleus of an atom, defining the element's identity.

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Example: This diagram shows a proton as a red, positively charged particle located with neutrons inside the atom's central nucleus, distinguishing it from orbiting electrons.

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Atomic Number Noun

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[uh-tom-ik num-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 on the periodic table.

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Example: This diagram shows an atom's parts. The atomic number is the count of protons (green spheres) in the central nucleus, which is 6 here.

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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 net electric charge (neutral) that is found in the nucleus of an atom.

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Example: This diagram shows a neutron, a particle with no charge, located inside the atom's central nucleus along with protons.

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Mass Number Noun

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[mass num-ber]

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Mass Number

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The total count of protons and neutrons combined within a single atom's nucleus, representing its approximate atomic mass.

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Example: This image shows that the mass number (27) of an aluminum atom is the total count of its protons (13) and neutrons (14).

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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 that have an equal number of protons but different numbers of neutrons.

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Example: This image shows three forms of Hydrogen. Each has one proton, but they have different numbers of neutrons, which makes them isotopes of each other.

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Radioactive Adjective

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[rey-dee-oh-ak-tiv]

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Radioactive

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The property of an unstable atomic nucleus that causes it to spontaneously decay, emitting radiation to become more stable.

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Example: This graph shows that for a radioactive substance, the amount remaining decreases by half after each 'half-life' period passes, starting from 100%.

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Ion Noun

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[ahy-on]

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Ion

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An atom or molecule that has acquired a net electrical charge by either losing or gaining one or more electrons.

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Example: This diagram shows an atom with more protons (4) than electrons (3), making it a positively charged ion, or cation.

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Cation Noun

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[kat-ahy-on]

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Cation

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A type of ion that possesses a positive electrical charge, which is formed when a neutral atom loses electrons.

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Example: A neutral sodium atom loses an electron from its outer shell, becoming a positively charged sodium ion (Na+), which is a cation.

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Anion Noun

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[an-ahy-on]

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Anion

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A type of ion that possesses a negative electrical charge, which is formed when a neutral atom gains electrons.

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Example: A neutral chlorine atom gains one electron to become a negatively charged chloride ion, which is an example of an anion.

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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 that orbits the nucleus of an atom in specific energy levels.

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