Unit 1: Properties of Matter

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Atom

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smallest unit into which matter can be divided without the release of electrically charged particles.

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Isotope

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any of two or more forms of a chemical element, having the same number of protons in the nucleus, or the same atomic number, but having different numbers of neutrons in the nucleus, or different atomic weights.

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Ion

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an electrically charged atom or group of atoms formed by the loss or gain of one or more electrons, as a cation (positive ion), which is created by electron loss and is attracted to the cathode in electrolysis, or as an anion (negative ion), which is created by an electron gain and is attracted to the anode.

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Subatomic Particles

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Any of various units of matter below the size of an atom, including the elementary particles and hadrons.

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Proton

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a positively charged elementary particle that is a fundamental constituent of all atomic nuclei.

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Neutron

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an elementary particle having no charge, mass slightly greater than that of a proton.

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Electron

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an elementary particle that is a fundamental constituent of matter, having a negative charge.

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Valence Electron

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an electron of an atom, located in the outermost shell (valence shell) of the atom, that can be transferred to or shared with another atom.

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Nucleus

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the positively charged mass within an atom, composed of neutrons and protons, and possessing most of the mass but occupying only a small fraction of the volume of the atom.

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Atomic number

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the number of units of positive charge (protons).