Unit 2 Vocab

  1. atom - smallest particle of an element that retains its identity in a chemical reaction
  2. atomic mass - a weighted average mass of the atoms in a naturally occurring sample of the element, reflecting both the mass and the relative abundance of the isotopes as they occur in nature
  3. atomic mass unit (amu) - one twelfth of the mass of a carbon-12 atom
  4. atomic number - the number of protons in the nucleus of an atom of that element
  5. cathode ray - glowing beam that travels within a cathode ray tube from the cathode (negative electrode) to the anode (positive electrode)
  6. Dalton's atomic theory - created from hypotheses and theories made by John Dalton to explain his observations; consists of four main ideas: 1) all elements are composed of tiny indivisible particles called atoms, 2) atoms of the same element are identical and the atoms of any one element are different from those of any other element, 3) atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds, 4) chemical reactions occur when atoms are separated, joined, or rearranged and atoms of one element are never changed into atoms of another element as a result of a chemical reaction
  7. electron - negatively charged subatomic particles
  8. group - aka family, each vertical column of the periodic table 
  9. isotopes - atoms that have the same number of protons but different numbers of neutrons 
    1. mass number - the total number of protons and neutrons in an atom
    2. neutron - subatomic particle with no charge but with a mass nearly equal to that of a proton
    3. nucleus - the tiny central core of an atom and is composed of protons and neutrons
    4. period - each horizontal row of the periodic table
    5. periodic table - an arrangement of elements in which the elements are separated into groups based on a set of repeating properties, allowing you to easily compare the properties of one element (or a group of elements) to another element (or group of elements)
    6. proton - positively subatomic particle with a mass of about 1840 times that of an electron
    7. alpha particle - a particle emitted by alpha radiation that contains two protons and two neutrons and and has a double positive charge
    8. band of stability - a region where the stable nuclei are located
    9. beta particle - an electron resulting from the breaking apart of a neutron in an atom
    10. film badge - a badge consisting of several layers of photographic film covered with black light-proof paper, all encased in a plastic or metal holder that must be worn for the entire duration of work as an important radiation detector for people who work near any type of radiation source
    11. fission - when the nuclei of certain isotopes are bombarded with neutrons, splitting the nucleus into smaller fragments
    12. fusion - when nuclei combine to produce a nucleus of greater mass (more energy is released from the combination of small nuclei in fusion than the splitting of large nuclei in fission)
    13. gamma ray - a high-energy photon emitted by a radioisotope
    14. Geiger counter - uses a gas-filled metal tube to detect radiation; can detect alpha, beta, and gamma radiation
    15. half-life - the time required for one-half of the nuclei of a radioisotope sample to decay to products
    16. ionizing radiation - radiation with enough energy to knock electrons off some atoms of the bombarded substance to produce ions
    17. neutron absorption - the process that decreases the number of slow-moving neutrons, uses control rods made of materials like cadmium
    18. neutron activation analysis - a procedure used to detect trace amounts of elements in samples
    19. neutron moderation - the process that slows down neutrons so the reactor fuel (uranium-235 or plutonium-239) captures them to continue the chain reaction, necessary as most neutrons produced move so fast they will pass right through a nucleus without being absorbed, works well with the moderators water and carbon as graphite 
    20. positron - a particle with the mass of an electron but a positive charge 
    21. radiation - the penetrating rays and particles emitted by a radioactive source
    22. radioactivity - the process by which materials give off rays
    23. radioistopes - the nuclei of unstable isotopes
    24. scintillation counter - uses a phosphor-coated surface to detect radiation, designed to detect all types of ionizing radiation
    25. transmutation - the conversion of an atom of one element to an atom of another element through either radioactive decay or the bombardment of the nucleus of an atom by particles
    26. transuranium elements - the elements in the periodic table with atomic numbers above 92 (the atomic number of uranium) which all undergo transmutation