1. Nitrogen
  2. Helium
  3. Lithium
  4. Hydrogen
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Option 4 : Hydrogen

  • The lowest atomic mass of the elements is hydrogen.
  • The Atomic Mass is the sum of the mass of protons and neutrons present in the atom of the element.
  • The atomic mass of hydrogen is 1 unit, Helium is 2 units, Lithium is 3 units and that of Nitrogen is 7 units.
  • The elements are arranged in the periodic table in the increasing order of their atomic masses.
  • Hydrogen is the first element in the Periodic Table.
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