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Across 2. Created the first scientific atomic theory; last name only 5. The abbreviation for units we use for the relative mass of atoms; 1/12th of a Carbon-12 atom 8. The positive particle in an atom's nucleus 9. The negative particle in an atom, found in clouds around the nucleus 13. "Discovered" the nucleus; last name only 14. The identity of an element; the number of protons in the nucleus of an atom (two words) 15. Matter cannot be created or destroyed 16. Smallest unit of an element that maintains the properties of that element 17. Atoms of the same element that have different masses

Down 1. General term for any isotope of any element 3. The neutral particle in an atom's nucleus 4. The number of protons and neutrons in the nucleus of an isotope (two words) 6. Determined that electrons orbit at specific energy levels around the nucleus; last name only 7. Short range force that holds the nuclear particles together (two words, no space) 10. Greek who first used the term "atomos" 11. average _____________________ is the weighted average of the atomic masses of isotopes of an element 12. "Discovered" electrons; last name only