nucleus, in physics: Size and Density

The nucleus occupies only a tiny fraction of the volume of an atom (the radius of the nucleus being some 10,000 to 100,000 times smaller than the radius of the atom as a whole), but it contains almost all the mass. An idea of the extreme density of the nucleus is revealed by a simple calculation. The radius of the nucleus of hydrogen is on the order of 10⁻¹³ cm so that its volume is on the order of 10⁻³⁹ cm³ (cubic centimeter); its mass is about 10⁻²⁴ g (gram). Combining these to estimate the density, we have 10⁻²⁴ g/10⁻³⁹ cm³ ≈ 10¹⁵ g/cm³, or about a thousand trillion times the density of matter at ordinary scales (the density of water is 1 g/cm³).

Sections in this article:

• Introduction
• Scientific Investigations of the Nucleus
• Scientific Notation for the Nucleus and Nuclear Reactions
• Models of the Nucleus
• Mass Defect, Binding Energy, and Nuclear Reactions
• Size and Density
• Composition
• Bibliography

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