CHEMISTRY

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Across
  1. 2. An atomic model that proposes electrons move in fixed energy levels
  2. 6. Weak forces of attraction between molecules
  3. 7. A substance that increases the rate of reaction by providing an alternative pathway
  4. 9. The minimum energy required to start a chemical reaction
Down
  1. 1. The total number of protons and neutrons in an atom
  2. 2. A substance that accepts a proton
  3. 3. The minimum energy required to remove one electron from a gaseous atom
  4. 4. The region around the nucleus where there is a high probability of finding an electron
  5. 5. A covalent bond formed when one atom donates both electrons
  6. 8. The electrostatic force of attraction between positive and negative ions