1.1.8 Size & Mass of Atoms

The Size of the Nucleus Compared to the Atom

• Size Comparisons:
  • The radius of an atom is approximately 0.1 nanometers (nm) or 1 × 10⁻¹⁰ meters (m).
  • The radius of the nucleus is even smaller, about 1 × 10⁻¹⁴ meters (m), which is less than 1/10,000 of the atom's radius.
• Contextual Comparisons:
  • For perspective, the radius of a typical bacterium is about 1 × 10⁻⁶ meters (m), which is much larger than the size of an atom.
  • The radius of a human hair is approximately 1 × 10⁻⁴ meters (m), which is significantly larger than even a bacterium.

Masses of Subatomic Particles

• The masses of subatomic particles are extremely small. Instead of expressing their actual masses in kilograms, we use their relative masses for simplicity.

Relative Mass and Charge of Subatomic Particles:

Subatomic Particle	Relative Mass	Relative Charge
Proton	1	+1
Neutron	1	0
Electron	Very small	-1