Words that I learned in Science

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Across
  1. 3. a column in the periodic table, the group number equals the number of electrons in the outer shell
  2. 6. a group of rare gases
  3. 7. any of a series of 15 consecutive chemical elements in the periodic table
  4. 10. center of atom
  5. 14. found in the shells and has negative charge
  6. 15. the electrons in the outermost shell, or energy level, of an atom
  7. 18. physical substance
  8. 19. elements that constitute Group 17
Down
  1. 1. a one or two letter symbol that represents the element
  2. 2. an element that is generally a poor conductor of heat and electricity
  3. 4. inside a nucleus and has a positive charge
  4. 5. a row in the periodic table, the row number equals to the number of shells
  5. 8. having the properties of an alkali, or containing alkali; having a pH greater than 7.
  6. 9. the number of protons and neutrons combined
  7. 10. inside of the atom and has no charge
  8. 11. chemical substance that cannot be broken down into other substances
  9. 12. the number of protons
  10. 13. rings outside of an atom
  11. 16. a substance that contains two or more elements chemically combined in a fixed proportion
  12. 17. a type of chemical element which has a preponderance of properties in between