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Across 4. Credited with the earliest formulation of the Atomic Theory. 5. A subatomic particle with a negative charge. 6. Form when atoms or ions join together to make a new substance. 8. Composed of atoms which have the same atomic number. 9. The number of protons in a element. (2 Words) 10. Total number of protons and neutrons. (2 Words) 13. Atoms with the same number of protons, but a different number of neutrons. 15. A subatomic particle with a positive charge.

Down 1. The measure an elements combining power when it forms chemical compounds or molecules. 2. Developed the Bohr model of the atom. 3. Composed the earliest speculation of the atom. 7. Credited with the discovery of the nucleus. 11. The center of all atoms. Contains the protons and neutrons. 12. A subatomic particle with no charge. 14. Smallest representative unit of an element.