Xword clues chapter 19-20

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Across
  1. 3. bond formed when atoms share electrons
  2. 5. substances that form as a result of a reaction
  3. 6. substances that exist before the reaction begins
  4. 8. a reaction that releases heat energy
  5. 12. symbol with dots to show electron in outer energy level
  6. 14. large protein molecules that change the rate of a reaction in your body so that cells can work properly
  7. 16. a charged atom
  8. 17. the group of elements that have stable outer energy levels
  9. 18. bond in which electrons are shared unevenly
  10. 20. pure substance containing two or more elements that are bonded
  11. 22. energy needed to start a reaction
  12. 23. chemical symbols and numbers that shows type and how many of each element are present
Down
  1. 1. bonds when metal atoms share pooled electrons
  2. 2. how fast a reaction occurs
  3. 3. a process that produces a new substance
  4. 4. a reaction that absorbs heat energy
  5. 7. a polar covalent molecule with two hydrogen atoms, one oxygen atom
  6. 9. force that holds two atoms together
  7. 10. tells chemists the reactants, products, physical state, and proportions of each substance present
  8. 11. shows the number of atoms of an element present in a compound
  9. 13. the law that states: in a closed system, mass of reactants must equal the mass of product
  10. 15. amount of substance present in a certain volume
  11. 16. bond formed by two charged atoms (usually a metal and a nonmetal)
  12. 19. type of change that produces a new substance
  13. 21. neutral particle formed when atoms share electrons