Multiple choice general knowledge

Which is the lightest of all the elements and has the atomic number 1?

  1. Oxygen

  2. Carbon Dioxide

  3. Carbon Monoxide

  4. Hydrogen
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D Correct answer
Explanation

Hydrogen is the lightest element with atomic number 1 and atomic mass of approximately 1.008 u. It is the most abundant element in the universe and the simplest atom, consisting of just one proton and one electron. Oxygen, carbon dioxide, and carbon monoxide are all heavier, with carbon dioxide and carbon monoxide being compounds, not elements.

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