Which of the following elements has the lowest atomic mass?

• A. Beryllium (Be)
• B. Helium (He)
• C. Lithium (Li)
• D. Hydrogen (H)

Answer: (D)

Verified step by step guidance

1. Step 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. Step 2: Identify the atomic masses of the given elements: Beryllium (Be), Helium (He), Lithium (Li), and Hydrogen (H). These values can be found on the periodic table.
3. Step 3: Compare the atomic masses of each element. Hydrogen has an atomic mass close to 1 amu, Helium about 4 amu, Lithium about 7 amu, and Beryllium about 9 amu.
4. Step 4: Recognize that the element with the lowest atomic mass is the one with the smallest number of protons and neutrons, which is Hydrogen in this case.
5. Step 5: Conclude that Hydrogen (H) has the lowest atomic mass among the listed elements.