Atomic nucleus
An atomic nucleus is the compact central part of an atom, made from protons and neutrons. Nearly all of an atom’s mass is concentrated there.
How big is it?
10 fm · characteristic size
Characteristic size · representative
A little perspective
Atomic nucleus vs Proton: length comparison
The characteristic size of an atomic nucleus is about 5.95 times the diameter of a proton.
An atomic nucleus is the compact central part of an atom, made from protons and neutrons.
A proton is a positively charged particle found in the nucleus of atoms, made up of quarks.
Both rulers start at the same zero and share one linear scale. Artwork keeps its original proportions.
Measurements, assumptions & sources +
Atomic nucleus
Characteristic size: 10 fm; representative.
A 10 fm diameter scale model of a heavy nucleus. Nuclear size depends on the number of nucleons.
University of Utah — Cell size and scale
The marked characteristic size is calibrated. Unmeasured illustration details are representative.
Proton
Diameter: 1.682 fm; measured constant.
Twice the approximately 0.8409 fm charge radius. The charge distribution has no hard boundary; the illustration is schematic.
NIST — 2022 CODATA fundamental constants
The marked diameter is calibrated. Unmeasured illustration details are representative.
Use the visual comparison to explore its scale, then check the measurements and sources.
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Why this measurement?
Why we use 10 fm
We compare the characteristic size of an atomic nucleus. This is a representative comparison value; individual specimens or conditions can vary.
A 10 fm diameter scale model of a heavy nucleus. Nuclear size depends on the number of nucleons.
The marked horizontal span follows the measured feature, not the edges of the image. How calibrated comparisons work →
Recorded properties
Dimensions and measurements
| Property | Selected value | Recorded range | Basis |
|---|---|---|---|
| 10 fm | Not recorded | representative |
Around this scale
Explore nearby values.
Compare examples with lower, similar and higher values. Each card names the measurement being compared.
Nearest lower valueFundamental physicsProton1.682 fmDiameterA proton is a positively charged particle found in the nucleus of atoms, made up of quarks.
Nearest higher valueFundamental physicsElectron2.426 pmCompton wavelengthAn electron is a fundamental subatomic particle with a negative electric charge, found in atoms and responsible for electricity and chemical bonding.Sources and method
Want to check the number?
The source records and measurement method remain available for inspection.
- University of Utah — Cell size and scaleApproximate biological size regimes. Atlas specimens and geometric assumptions are individually labelled.
More ways to see it
Curated comparisons
There’s always another scale
Follow your curiosity.
Fundamental physicsProton1.682 fmA proton is a positively charged particle found in the nucleus of atoms, made up of quarks.
MicroscopicCell10 µmA cell is the basic structural unit of living organisms.
PeopleHair70 µmA hair is a slender strand of protein that grows from the skin of humans and other mammals.Fundamental physicsElectron9.109 × 10⁻³¹ kgAn electron is a fundamental subatomic particle with a negative electric charge, found in atoms and responsible for electricity and chemical bonding.
Fundamental physicsBohr radius52.92 pmThe Bohr radius is a fundamental physical constant representing the most probable distance between the nucleus and the electron in a hydrogen atom according to early quantum theory.MicroscopicHydrogen atom105.8 pmA hydrogen atom is the simplest neutral atom, with one proton in its nucleus and one electron around it.
MicroscopicWater molecule280 pmA water molecule is a group of two hydrogen atoms bonded to one oxygen atom.
MicroscopicGlucose molecule1 nmA glucose molecule is a simple sugar used by living cells as a source of chemical energy.