Across
- 3. Physical substance in general
- 5. the centeral and most important part
- 6. number The number of protrons in the nucleus
- 9. found in all atoms
Down
- 1. each of two forms of the same element
- 2. A part or aspect of something abstract
- 3. number the total number of protrons
- 4. about the same mass as a protron
- 7. an atom or molecule
- 8. a stable particle occuring