Chemistry!

12345678910
Across
  1. 2. basic unit of matter
  2. 4. tightly packed
  3. 7. no volume or shape
  4. 8. a pure substance
  5. 10. chemical compounds
Down
  1. 1. something that allows flow
  2. 3. something joined by chemical bond
  3. 5. a mixture of things
  4. 6. central core of an atom
  5. 9. all elements