Science Review Crossword

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Across
  1. 1. the electrons in the outermost energy level of an atom
  2. 3. the number of valence electrons in an atom of argon
  3. 5. the number of valence electrons in an atom of sodium
  4. 7. the name of the elements in group 18; they are nonreactive
  5. 9. a chemical combination of two or more atoms
  6. 11. found in the nucleus of an atom with a neutral charge
  7. 12. found in the nucleus of an atom with a positive charge
  8. 13. the number of valence electrons in an atom of oxygen
Down
  1. 2. particles located outside the nucleus with a negative charge
  2. 3. a substance made up of only one type of atom; found on the periodic table
  3. 4. these are the horizontal rows on the periodic table
  4. 6. these are the vertical columns on the periodic table
  5. 8. the number of valence electrons in an atom of chlorine
  6. 10. elements in the same group have similar ____ because they have the same number of valence electrons