Periodic table

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Across
  1. 2. The smallest unit of matter, consisting of protons, neutrons, and electrons.
  2. 3. The central part of an atom containing protons and neutrons.
  3. 5. The maximum number of electrons in the third shell of an atom (before the next shell starts filling).
  4. 7. Elements in the same vertical column of the periodic table are in the same __________.
  5. 9. The negatively charged particle that orbits the nucleus of an atom.
  6. 10. The number of protons in an atom’s nucleus is also called its __________ number.
Down
  1. 1. The subatomic particle with no charge, found in the nucleus.
  2. 4. The maximum number of electrons in the second shell of an atom.
  3. 6. The maximum number of electrons in the first shell of an atom.
  4. 8. A row in the periodic table is called a __________.