Calculator Inputs
Enter mass number and neutron count to compute the isotope atomic number. Optional fields add checks, ion details, and sample totals.
Example Data Table
| Isotope | Mass Number (A) | Neutrons (N) | Atomic Number (Z) | Element | Charge | Electrons |
|---|---|---|---|---|---|---|
| Carbon-14 | 14 | 8 | 6 | Carbon | 0 | 6 |
| Chlorine-37 | 37 | 20 | 17 | Chlorine | -1 | 18 |
| Sodium-23 | 23 | 12 | 11 | Sodium | +1 | 10 |
| Iron-56 | 56 | 30 | 26 | Iron | +2 | 24 |
| Uranium-235 | 235 | 143 | 92 | Uranium | 0 | 92 |
Formula Used
The calculator uses the nuclear identity relationship that mass number equals protons plus neutrons. Once neutrons are known, subtracting them from mass number gives the atomic number directly.
How to Use This Calculator
- Enter the isotope mass number.
- Enter the neutron count.
- Add ion charge if the isotope is not neutral.
- Optionally add a known atomic number to verify your answer.
- Optionally add abundance and sample atoms for deeper calculations.
- Click the calculate button.
- Review the result cards, notation, chart, and downloadable outputs.
FAQs
1. What does atomic number mean for an isotope?
Atomic number is the number of protons in the nucleus. Every isotope of the same element has the same atomic number, even when neutron counts differ.
2. How do I find atomic number from mass number and neutrons?
Subtract neutrons from the mass number. The result is the atomic number, which also equals the number of protons in that isotope.
3. Why do isotopes of one element have different masses?
Isotopes differ by neutron count. Since mass number equals protons plus neutrons, adding or removing neutrons changes mass without changing element identity.
4. Does ion charge change the atomic number?
No. Ion charge changes only the number of electrons. Atomic number depends on protons, so it stays constant unless the nucleus changes.
5. Can this calculator identify the element name too?
Yes. When the calculated atomic number matches an element in the periodic table range, the calculator returns the element name and symbol automatically.
6. What if neutrons are larger than the mass number?
That input is physically invalid for a normal isotope entry. The calculator flags it because mass number must always include all protons and neutrons together.
7. What is isotope notation?
Isotope notation places mass number as a superscript and atomic number as a subscript beside the element symbol. Charge may appear as an additional superscript.
8. When is neutron to proton ratio useful?
It helps compare nuclear composition and stability trends. Heavier elements usually need more neutrons relative to protons to remain stable.