Unit 5

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Across
  1. 1. reduce the amount of activation energy that is needed for a reaction to take place
  2. 5. the simplest particle of an element
  3. 8. one or more substances change to produce on or more different substances
  4. 10. is anything that occupies space and has mass
  5. 11. the ability to do work
  6. 12. central region, makes up the bulk of the mass
  7. 14. when two atoms share one or more pairs of electrons
  8. 17. are attractive forces that hold atoms together
  9. 20. proceed in only one direction
Down
  1. 2. number of protons
  2. 3. is a three dimensional region around a nucleus that indicates that probable location of an electron
  3. 4. sodium ion and chloride ion attract each other
  4. 6. is the simplest part of a substance the retains all of the properties
  5. 7. the amount of energy needed to start the reaction
  6. 9. made up of atoms of two or more elements in fixed proportions
  7. 10. an atom is equal to the total number of protons an neutrons of an atom
  8. 13. negatively charged particles
  9. 15. are substances that cannot be broken down chemically into simpler kinds of matter
  10. 16. atoms of the same element that have a different number of neutrons
  11. 18. an atom or molecule with an electrical charge
  12. 19. is the quantity of matter an object has