Periodic table

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Across
  1. 2. Electrons in the outermost shell of an atom
  2. 5. Half the distance between the nuclei of atoms bonded
  3. 6. Group of elements known to be in group 17
  4. 8. The measure of an atoms ability to attract electrons
Down
  1. 1. The group of elements known for being in group 18
  2. 3. A subatomic particle with a negative charge
  3. 4. energy The energy required to remove an electron
  4. 7. A vertical columns in the periodic table