Atomic structure and electronic configuration

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Across
  1. 2. element with the same number of protons, but a different number of neutrons
  2. 4. total number of protons and neutrons
  3. 6. number of protons
  4. 7. The atom gains or loses electrons, becoming charged
Down
  1. 1. basic building block of all matter
  2. 3. The central core containing protons and neutrons
  3. 5. anything smaller than an atom