Science crossword puzzle

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Across
  1. 3. The biggest planet in the solar system
  2. 7. Positively charged ______ attached to negative electrons to form the first atoms
  3. 9. First atom formed after the big bang
  4. 10. Number of planets in the solar system
Down
  1. 1. Second atom formed after the big bang
  2. 2. Farthest planet from the sun
  3. 4. 3rd planet from the sun
  4. 5. Form that energy was released from attachment of positive protons and negative electrons
  5. 6. Once it slowed down it turned to matter after
  6. 8. Planet with the most moons