Know your chemistry

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Across
  1. 2. A metal element that is essential for human. It plays a key role in skin health, immune system, and cell growth.
  2. 4. Atoms that have different number of neutron.
  3. 7. A number that is a sum of proton and neutron.
  4. 9. A negative charge particle in an atom.
Down
  1. 1. A metal element that is essential for your bone health.
  2. 3. The name of the diagram that shows an atom's structure.
  3. 5. An element that has 8 protons.
  4. 6. The letter in each block of the periodic table.
  5. 8. The first letter of this noble gas is A.