science review (mass)

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Across
  1. 2. a horizontal row of the periodic table
  2. 4. person who made discoveries of the electron and radioactivity led to different models for the structure of the atom
  3. 6. the development of the idea of atoms and their structure
  4. 8. equivalent to the number of protons and neutrons in the atom
  5. 9. a solid material that is typically hard, shiny, malleable, and ductile, with good electrical and thermal conductivity
  6. 11. negatively charged subatomic particle
  7. 13. a substance that takes part in and undergoes change during a reaction.
  8. 15. an outer shell electron that is associated with an atom
  9. 17. molecules composed of atoms from more than one element held together by chemical bonds
  10. 20. skewed number of protons and electrons
  11. 24. an element incapable of forming simple positive ions in solution
  12. 25. the mass of an atom of a chemical element expressed in atomic mass units
  13. 26. most reactive families on the periodic table
  14. 28. believed empty space didn’t exist and all matter was made of the four elements
  15. 29. a material made up of two or more different substances which are mixed but are not combined chemically
  16. 30. made of protons and neutrons, the center of an atom
  17. 31. when proton and neutron count of an element stays the same but the electron count varies
  18. 32. credited with the discovery and identification of the electron; and with the discovery of the first subatomic particle
Down
  1. 1. column of elements in the periodic table
  2. 2. a table of the chemical elements arranged in order of atomic number
  3. 3. neutral subatomic particle
  4. 5. mixture having a non-uniform composition
  5. 7. area where electrons orbit the nucleus of an atom
  6. 10. positively charged subatomic particle
  7. 12. person who made a more abstract theory of matter and named the term "atomos" or "atoms" to label the particles
  8. 14. to undergo a chemical reaction with another atom, molecule, or compound
  9. 16. system is neither created nor destroyed by chemical reactions or physical transformations
  10. 18. Ancient Greek philosopher remembered today for his idea of the atomic theory
  11. 19. substances that are made of only one type of atom or only one type of molecule
  12. 21. the father of nuclear physics
  13. 22. mixture that has the same proportions of its components throughout any given sample
  14. 23. an element whose properties are intermediate between those of metals and solid nonmetals
  15. 27. atoms having the same number of protons in their atomic nuclei