Atomic structure & periodic table

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Across
  1. 1. Atomic ——- describes the weighted average of protons and neutrons
  2. 3. Spherical electron orbital with capacity for one electron pair
  3. 9. The periodic table elements that decrease in size and increase in density from left to right
  4. 11. Non-SI unit describes size of atoms (= 100 pm)
  5. 12. Basic unit of matter for elements
  6. 13. Ancient Greek for indivisible
  7. 17. Tiny and dense centre of atom containing protons and neutrons
  8. 18. Class of atom with the same number of protons but varied neutrons
  9. 19. Electron orbital-pair capacity steps in —- numbers (s-1 p-3 d-5 f-7)
  10. 20. Component of the atomic nucleus (eg. proton)
  11. 21. 80% of all elements
  12. 22. Element that may naturally exist as a pure substance (Ag with Atomic number 47)
Down
  1. 2. Most common isotope contains one proton and no neutron
  2. 4. Negatively charged sub-atomic
  3. 5. In the nucleus, the atomic number
  4. 6. Author of modern periodic table development
  5. 7. Chemical symbol for nickel
  6. 8. Current ———- -mechanical model of the atom
  7. 10. Outer-most electron cell compared with noble gas
  8. 11. Atomic Mass Unit is a Non-SI unit mass of one proton (also dalton as 1/12 mass C-12)
  9. 13. Neutral particle emitted during radioactive decay
  10. 14. ——— Number is constant for elements,
  11. 15. The periodic table’s column of elements that increase in size and similar reactivity
  12. 16. Theorist of concentric shells to model electron energy levels