Chemistry crossword

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Across
  1. 2. Type of electromagnetic radiation that can be perceived by the human eye.
  2. 5. Name that is the reference for the value of the mole.
  3. 8. Has two shells and the same number of valence electrons of chlorine.
  4. 10. Protons and neutrons particles.
  5. 11. Has a greenish light with the flame test.
  6. 13. Father of modern chemistry.
  7. 17. Level of energy when electrons orbit.
  8. 18. Every element has a specific mass as a signature.
  9. 20. Electrons located on the outermost shell
  10. 23. Variant of a same element.
Down
  1. 1. Discovered the positive nucleus in the atom.
  2. 3. Unit that represents a large set of particles.
  3. 4. An unstable isotope that will start a chain reaction.
  4. 6. First known as "better air".
  5. 7. Radiation that shows the highest level of energy on the spectrum.
  6. 9. Electrons located on the first shell(s) but not the last one.
  7. 12. An old concept that was believed to be a fluid taken or added during combustion.
  8. 14. From its Latin origin "Aurum"
  9. 15. Radiation that shows the lowest level of energy on the spectrum.
  10. 16. Has a mass of 56 amu.
  11. 19. Has two shells of energy and only four valence electrons.
  12. 21. Isotope of hydrogen with an extra two neutrons
  13. 22. Discover the levels of energy for the electrons.