---
title: "Properties of Nuclei and the Nuclear Force"
description: "Nuclear radius grows with the cube root of nucleon number, so nuclear density is nearly constant, and the force holding nucleons together is short ranged and blind to charge. Those two facts shape the"
canonical: https://lightmysky.com/learn/science/properties-of-nuclei-and-the-nuclear-force-mt_HdMS_muGWa
source: https://lightmysky.com/learn/science/properties-of-nuclei-and-the-nuclear-force-mt_HdMS_muGWa.md
retrieved: 2026-09-12
---

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# Properties of Nuclei and the Nuclear Force

Nuclear radius grows with the cube root of nucleon number, so nuclear density is nearly constant, and the force holding nucleons together is short ranged and blind to charge. Those two facts shape the binding energy curve.

Subject: Science · Area: Quantum & Modern Physics · Ages 19 to 21
Page: https://lightmysky.com/learn/science/properties-of-nuclei-and-the-nuclear-force-mt_HdMS_muGWa

## Ready when they can

- Estimates a nuclear radius and density from the nucleon number
- Describes the range and charge independence of the strong force
- Explains why the binding energy per nucleon peaks near iron

## Lesson: Tiny cores, enormous densities

A nucleus packs Z protons and N neutrons, with A the total, into a radius near 1.2 fm times the cube root of A. Carbon 12 holds 6 protons and 6 neutrons. Since volume grows with A, every nucleus shares nearly the same enormous density.

The strong force grips across a few femtometers, then fades and lets electric repulsion rule. It holds protons and neutrons almost equally, which mirror nuclei confirm: swap the counts and the binding barely changes. Light nuclei match protons with neutrons, while heavy ones past Z 15 carry extra neutrons as dilution against proton repulsion.

**Example.** Try A equals 8. Its cube root is 2, so the radius is about 2.4 fm. Binding energy per nucleon climbs with size to a peak near iron, then falls, so light nuclei gain by fusing and heavy ones by splitting.

**Tip.** Read the curve, not just the size: the most tightly bound nuclei sit near the iron peak, and that is where fusion stops paying and fission starts.

**Recap.** Density stays flat, the force stays short and charge blind, and binding per nucleon peaks near iron.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Mass Defect and Binding Energy per Nucleon](https://lightmysky.com/learn/science/mass-defect-and-binding-energy-per-nucleon-mt_UdYE8hgXyl)
- [Relativistic Momentum and Energy](https://lightmysky.com/learn/science/relativistic-momentum-and-energy-mt_zBq87F-j3B)

## Opens up

- [Nuclear Models: the Liquid Drop and the Semi-Empirical Mass Formula](https://lightmysky.com/learn/science/nuclear-models-the-liquid-drop-and-the-semi-empirical-mass-formula-mt_-cTGNdUJLz)
- [Decay Modes, Decay Chains and Nuclear Reactions](https://lightmysky.com/learn/science/decay-modes-decay-chains-and-nuclear-reactions-mt_b_imidwJeQ)