Ishan Chemistry Puzzle - 1

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Across
  1. 5. Element in periodic table with atomic number 4
  2. 6. Element in periodic table with atomic number 12
Down
  1. 1. Element in periodic table with atomic number 3
  2. 2. - Element in periodic table with atomic number 2, available in plenty in Sun
  3. 3. - Element in periodic table with atomic number 29, used in electrical wires
  4. 4. Element in periodic table with atomic number 20, forms our bone