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anything that has mass and takes up space


very small particle that make up all matter


a region that is located at the center of an atom and contains most of the atom's mass


a positively charged particle located din the nucleus


a neutral particle, which has no charge, located in the nucleus


negatively charged particle that moves in the space surrounding the nucleus

spectral line

is a single wavelength of light that can be seen when the light from an excited element is passed through a prism

energy levels

these regions of space in which electrons can move about the nucleus of an atom

electron cloud

region surrounding an atomic nucleus where an electron is most likely to be found


a pure substance made from atoms that all have the same number of protons

atomic number

shows some elements with their atomic numbers

mass number

sum of the number of protons and neutrons the atom has


atoms of the same element that contain different numbers of neutrons

average atomic mass

an element is the weighted average mass of the mixture of an element's isotopes


is an atom that is no longer neutral because it has gained or lost electrons

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