They make up EVERYTHING!

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Across
  1. 3. Neutral particle found in the nucleus
  2. 5. Electrons in the outermost energy level
  3. 8. The smallest unit of matter that keeps the properties of an element
  4. 14. The closest area to Earth where Hydrogen is undergoing fusion
  5. 15. Atoms of the same element with different numbers of neutrons
  6. 16. A bond formed between two non-metals
  7. 17. An atom that has gained electrons
  8. 19. A chart that organizes all known elements
  9. 20. A charged atom
  10. 21. The center of an atom
  11. 22. Very large stars that explode at the end of their lives
Down
  1. 1. The process where smaller atomic nuclei combine to form larger ones
  2. 2. The number of protons in an atom
  3. 4. Negatively charged particle that moves around the nucleus
  4. 6. The first and simplest element to exist in the universe
  5. 7. A group of atoms bonded together
  6. 9. A massive explosion that forms elements heavier than iron
  7. 10. The total number of protons and neutrons in an atom
  8. 11. The horizontal rows of the periodic table that show energy levels
  9. 12. Positively charged particle found in the nucleus
  10. 13. An atom that has lost electrons
  11. 14. Where fusion happens and new elements are formed
  12. 18. A bond formed between a metal and a non-metal
  13. 23. The vertical columns of the periodic table that show valence electrons