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Across 2. region in an atom where electrons are found (2 Words) 6. chemical compounds that give up hydrogen cations when they are dissolved in water 9. the force of attraction within atoms, ions, or molecules (2 Words) 10. occur when electrons are shared between two nearby atoms (2 Words) 11. any of the elements found in group 18 at the far right of the periodic table (2 Words) 12. used to represent the elements (2 Words) 15. reactive nonmetals having seven valence electrons 16. the number of protons in an atoms nucleus (2 Words) 17. a vertical column in the periodic table 18. indicates how many atoms of each element there are 19. extremely dense positively charged part of an atom in the center of the atom 20. the sum of the protons and neutrons (2 Words)

Down 1. the amount of energy need to remove the outermost electrons from an atom (2 Words) 3. system used for naming chemical substances (2 Words) 4. the electrons in the outermost energy level of an atom (2 Words) 5. a horizontal row in the periodic table 7. an atom or molecule that has lost or gained one or more of its outer electrons 8. positively charged particles in the nucleus 12. nonmetal with 4 valence electrons (2 Words) 13. ions of a single element (2 Words) 14. particles in an atom that have no charge