Science crossword puzzle thingy

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Across
  1. 3. Matter that can vary in composition.
  2. 4. _______ are one of the parts of making up the nucleus.
  3. 5. Most elements are __________.
  4. 7. A part of an atom that has protons and neutrons in it.
  5. 9. Anything that has mass and takes up space.
  6. 11. Matter with a composition that is always the same.
  7. 12. _________ is a compound composed of carbon and oxygen.
  8. 14. A small particle that is a building block of matter.
  9. 15. A mixture of water, sugar, and other substances.
  10. 16. _______ is another part of making up the nucleus.
  11. 17. _________ moving in an area outside a nucleus.
  12. 19. Each element on the ___________ consists of just one type of atom.
  13. 21. Having nothing else like it.
Down
  1. 1. A type of mixture in which the individual substances are evenly.
  2. 2. A type of mixture in which the individual substances are not evenly mixed.
  3. 6. A substance that consists of just one type of atom.
  4. 8. __________ is a million times greater than the diameter of an atom.
  5. 10. The combination of symbols and numbers that represents a compound is called a _________.
  6. 13. This element is a metalloid.
  7. 18. A type of substance containing atoms of two or more different element chemically bonded together.
  8. 20. To form a solution by mixing evenly.