Atomic Mass Calculator
Calculate atomic mass from protons and neutrons using the atomic mass formula
Calculate Atomic Mass
Atomic number (1-118)
Number of neutrons (0-177)
Atomic Mass Results
Mass Breakdown
Nuclear Stability Assessment
Likely stable nucleus
Unit Conversions
Atomic Mass Formula
Example: Carbon-12 Atomic Mass
Given Information
Element: Carbon-12 (most common carbon isotope)
Protons (Z): 6 (atomic number of carbon)
Neutrons (N): 6 (12 - 6 = 6)
Calculation
Atomic Mass = Z + N
Atomic Mass = 6 + 6
Atomic Mass = 12 u
This matches the definition: 1 u = 1/12 mass of carbon-12
Atomic Mass Units
Nuclear Stability
Quick Tips
Atomic mass ≈ protons + neutrons
Electrons contribute negligible mass
Mass number = atomic mass (rounded)
Binding energy causes small mass defect
Isotopes have same Z, different N
Understanding Atomic Mass
What is Atomic Mass?
Atomic mass is the total mass of an atom, including protons, neutrons, and electrons. However, since electrons are 1,836 times lighter than protons, they contribute negligibly to the total mass.
Key Components:
- • Protons: ~1 u each, positive charge
- • Neutrons: ~1 u each, no charge
- • Electrons: ~0.00055 u each, negative charge
- • Binding Energy: Slight mass loss (not included in this calculator)
Atomic Mass vs Mass Number
Atomic Mass
Actual mass of the atom in atomic mass units, including binding energy effects.
Mass Number (A)
Total number of protons and neutrons (always a whole number).
Why Do Atoms Need Neutrons?
Electrostatic Repulsion
Protons repel each other due to positive charge. This force tries to break the nucleus apart.
Strong Nuclear Force
Neutrons provide additional attractive force between nucleons, helping hold the nucleus together.
Nuclear Stability
The right neutron-to-proton ratio creates a stable nucleus that doesn't decay.
Real-World Applications
Nuclear Medicine
Isotopes with specific atomic masses are used for:
- • Medical imaging (Technetium-99m)
- • Cancer treatment (Iodine-131)
- • Radiocarbon dating (Carbon-14)
- • Nuclear power (Uranium-235)
Mass Spectrometry
Precise atomic mass measurements help:
- • Identify unknown compounds
- • Determine molecular structures
- • Measure isotopic abundances
- • Quality control in pharmaceuticals