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17 Cards in this Set

  • Front
  • Back
the smallest units of matter that retain the properties and characteristics of the element
subatomic particles
compose individual atoms
the dense central core of an atom; contains protons and neutrons
positively charged particles in nucleus
uncharged (neutral) particles in nucleus
tiny negatively charged particles that move about in a large space surrounding the nucleus
electron shell
certain regions around the nucleus in which electrons are most likely to move about
electron shell structure
first shell-never holds more than 2 electrons; second shell--holds a maximum of 8 electrons; third shell-can hold up to 18 electrons (3 more shells)
electrically neutra
the number of electrons in an atom of an element always equals the number of protons--balance each other
atomic number
the number of protons in the nucleus of an atom
mass number
the sum of an atom's protons and neutrons
atoms of an element that have different numbers of neutrons and different mass numbers--most are stable (nuclear structure does not change over time)
radioactive isotopes
unstable; their nuclei decay (spontaneously change)into a stable configuration
half-life of an isotope
the time required for half of the radioactive atoms in a sample of that isotope to decay into a more stable form
radioisotopes used to follow the movement of certain substances through the body; used in medical imaging procedures to diagnose and treat certain disorders
atomic mass unit
atomic mass
atomic weight of an element--average mass of all its naturally occurring isotopes