1. What is Exact Mass?

The exact mass of an isotope or molecule is calculated by summing the masses of the individual isotopes, weighted by their natural abundances. For monoisotopic mass, we use the most abundant isotope of each element.

2. How Does the Calculator Work?

The calculator uses the exact mass formula:

Where:

• \( \text{Isotope Mass} \) — Mass of the isotope in atomic mass units (amu)
• \( \text{Abundance} \) — Natural abundance of the isotope (as a decimal)

Explanation: The equation accounts for the weighted average of all naturally occurring isotopes of an element.

3. Importance of Exact Mass Calculation

Details: Exact mass is crucial in mass spectrometry for identifying molecules, distinguishing between compounds with similar nominal masses, and calculating isotopic distributions.

4. Using the Calculator

Tips: Enter isotope masses in amu and abundances as decimals (e.g., 0.989 for 98.9%). You can calculate for one isotope or add up to two isotopes in this version.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between exact mass and average mass?
A: Exact mass uses precise isotope masses, while average mass uses the weighted average of all isotopes.

Q2: How accurate should my mass values be?
A: For precise calculations, use isotope masses with at least 6 decimal places from authoritative sources.

Q3: What's monoisotopic mass?
A: The mass of a molecule calculated using the most abundant isotope of each element.

Q4: Why do abundances need to be decimals?
A: The calculation requires fractional abundances (e.g., 0.5 for 50%) rather than percentages.

Q5: Can I calculate for more than two isotopes?
A: This version handles up to two isotopes. For more complex calculations, specialized software is recommended.