What is the atomic mass of hydrogen?

The atomic mass of hydrogen (H) is approximately:

1.008 u (atomic mass units)

Why is it 1.008 and not exactly 1?

Hydrogen exists in three isotopic forms:

• Protium (¹H) → most abundant (~99.98%)
• Deuterium (²H)
• Tritium (³H)

The value 1.008 u is a weighted average of these isotopes based on their natural abundance.

Key Takeaway:

The atomic mass of hydrogen is 1.008 u, reflecting the average mass of its naturally occurring isotopes.