Calculator
Use any two of these three values: protons, neutrons, and mass number. Optional fields improve notation and ion interpretation.
Example Data Table
| Element | Symbol | Protons (Z) | Neutrons (N) | Mass Number (A) | Hyphen Notation |
|---|---|---|---|---|---|
| Hydrogen | H | 1 | 0 | 1 | H-1 |
| Carbon | C | 6 | 6 | 12 | C-12 |
| Carbon | C | 6 | 8 | 14 | C-14 |
| Sodium | Na | 11 | 12 | 23 | Na-23 |
| Chlorine | Cl | 17 | 20 | 37 | Cl-37 |
Formula Used
A = Z + N
N = A − Z
Z = A − N
Charge = Protons − Electrons
Here, A is mass number, Z is atomic number or proton count, and N is neutron count. Mass number includes only nucleons in the nucleus. Electrons are not included in the mass number.
How to Use This Calculator
- Enter any two values among protons, neutrons, and mass number.
- Add an element symbol or isotope notation if you want smarter identification.
- Optionally enter electrons or charge to classify the species as neutral, cation, or anion.
- Click Calculate Mass Number to show the result above the form.
- Review the calculated nucleon data, notation, charge behavior, and the Plotly graph.
- Use the CSV and PDF buttons to export the calculated report.
Frequently Asked Questions
1) What is the mass number of an atom?
Mass number is the total number of protons and neutrons inside the nucleus. It does not include electrons. Different isotopes of the same element have the same proton count but different neutron counts, so their mass numbers differ.
2) How is mass number different from atomic number?
Atomic number counts only protons. Mass number counts protons plus neutrons. Atomic number identifies the element itself, while mass number identifies a specific isotope of that element.
3) Do electrons affect the mass number?
No. Electrons do not change mass number because mass number only counts nucleons in the nucleus. You may add electron information to describe ions, but the mass number remains unchanged.
4) Can I find neutrons if I know mass number and protons?
Yes. Subtract the proton count from the mass number. The formula is N = A − Z. This calculator performs that step automatically when you provide those two values.
5) Why do isotopes have different mass numbers?
Isotopes of the same element always have the same number of protons, but they can contain different numbers of neutrons. That neutron difference changes the total nucleon count and therefore changes the mass number.
6) Can this calculator read isotope notation like C-14?
Yes. You can enter notation such as C-14 or 14C. The calculator uses that information to infer the element symbol and mass number, then completes missing values when enough data is available.
7) What does the N/Z ratio mean?
The N/Z ratio is neutrons divided by protons. It helps describe nuclear composition and is often used when comparing isotopes. It is not the mass number, but it helps interpret nucleus structure.
8) What happens if I enter inconsistent values?
The calculator checks whether protons plus neutrons equals mass number. If your entries conflict, it shows an error message instead of returning a misleading answer.