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Across 3. Transform from one form to another. 8. The smallest unit of matter that retains the identity of the substance. 9. The number of protons in the nucleus of an atom. This number identifies the atom 11. A characteristic of a substance that can be observed. 13. The central Part of the atom, containing protons and neutrons.

Down 1. the number of protons and neutrons in the nucleus of an atom. Mass number = protons + neutrons 2. the average mass number of all isotopes of an atom. Round this number to find the mass number of the atom. 4. Region surrounding the nucleus of an atom, where electrons are most likely to be found. 5. Ability to be stretched into a thin wire. 6. Subatomic particle with a negative charge and located outside the nucleus. 7. A substance that mixes with another substance evenly and dissolves. 10. subatomic particle with no charge, the same mass as a proton, and located in the nucleus of the atom. 11. subatomic particle with a positive charge and located in the nucleus of the atom. 12. Amount of matter contained in a substance.