Periodic table

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Across
  1. 2. Measure of an atom's ability to attract electrons in a chemical bond.
  2. 4. Energy required to remove an electron from an atom.
  3. 7. Series of elements in the periodic table with atomic numbers from 89 to 103.
  4. 8. Number of electrons in the outermost shell of an atom.
  5. 13. The repeating pattern of properties in the periodic table.
  6. 18. Number of protons in the nucleus of an atom.
  7. 19. Group of elements with partially filled d orbitals.
  8. 20. Group 17 elements known for their high reactivity.
Down
  1. 1. Series of elements in the periodic table with atomic numbers from 57 to 71.
  2. 3. To forecast the properties of undiscovered elements based on their position in the periodic table.
  3. 5. Russian chemist who developed the periodic table.
  4. 6. Element with properties intermediate between metals and nonmetals.
  5. 9. Organization of elements based on similar properties.
  6. 10. Group 1 element with a single valence electron.
  7. 11. Substance consisting of atoms with the same number of protons.
  8. 12. Group of elements with full outer electron shells, making them unreactive.
  9. 14. Principle stating that the properties of elements vary periodically with their atomic numbers.
  10. 15. Horizontal row in the periodic table.
  11. 16. Weighted average of the masses of an element's isotopes.
  12. 17. Vertical column in the periodic table.