The superscript preceding each hydrogen atomic symbol (H) represents which of the following?

• A. The number of neutrons in hydrogen
• B. The atomic number of hydrogen
• C. The number of valence electrons in hydrogen
• D. The mass number of the hydrogen isotope

Answer: (D)

Verified step by step guidance

1. Understand that the superscript preceding the hydrogen symbol (H) in isotopic notation represents a specific nuclear property of the atom.
2. Recall that the atomic number (Z) is the number of protons in the nucleus and is usually written as a subscript to the left of the element symbol, not as a superscript.
3. Recognize that the number of valence electrons is related to the electron configuration and is not represented by a superscript in the atomic symbol.
4. Know that the mass number (A) is the total number of protons and neutrons in the nucleus and is conventionally written as a superscript to the left of the element symbol.
5. Therefore, the superscript preceding the hydrogen symbol indicates the mass number of the hydrogen isotope, which differentiates isotopes by their neutron count.