Science word puzzle

12345678910111213
Across
  1. 2. a body of coherent matter
  2. 6. mass the of one oxygen atom
  3. 8. component of a whole thing
  4. 10. a positively charged elementary particle
  5. 12. number how many protons and electrons the element has
  6. 13. an elementary particle having no charge
Down
  1. 1. physics
  2. 3. a solid substance or body
  3. 4. number the integer nearest
  4. 5. an amount of space measured in cubic units
  5. 7. a particular kind of substance
  6. 9. also called negatron
  7. 11. a liquid substance
  8. 12. Smallest particle