Which element has the lowest atomic mass?

• A. Helium
• B. Lithium
• C. Carbon
• D. Hydrogen

Answer: (D)

Verified step by step guidance

1. Understand that atomic mass refers to the average mass of atoms of an element, measured in atomic mass units (amu), and is roughly equivalent to the number of protons and neutrons in the nucleus.
2. Recall or look up the atomic masses of the given elements: Helium, Lithium, and Carbon, noting that Hydrogen is not listed among the options but is mentioned as the correct answer.
3. Compare the atomic masses of Helium, Lithium, and Carbon to see which one is the smallest among them.
4. Recognize that Hydrogen, although not listed in the options, has an atomic mass of approximately 1 amu, which is lower than all the other elements mentioned.
5. Conclude that Hydrogen has the lowest atomic mass overall, even though it was not one of the options provided in the question.