The statement "In nature, the electric charge of any system is always equal to an integral multiple of the least amount of charge" is known as the quantization of electric charge.

Explanation:

Atomic Structure:

- Atoms are made up of three types of particles - protons, neutrons, and electrons.
- Protons have a positive charge, electrons have a negative charge, and neutrons have no charge.
- The charge on a proton and electron is exactly the same in magnitude but opposite in sign.
- The charge on a proton is taken as the unit of charge in the SI system, which is denoted as 'e'. The charge on an electron is -e.

Quantization of Electric Charge:

- Electric charge is quantized, which means it always exists as an integral multiple of the charge on an electron or a proton.
- Any object can have a net charge of only an integral multiple of the charge on an electron or a proton.
- This means that if an object has a net charge Q, then Q = ne, where n is an integer.

Proof of Quantization of Electric Charge:

- The quantization of electric charge was first observed by Robert Millikan in his oil drop experiment.
- In this experiment, he sprayed oil droplets into a chamber where they were exposed to X-rays, which caused them to become charged.
- The charged droplets were then placed in an electric field, which caused them to move.
- By measuring the electric field required to keep the droplets stationary, Millikan was able to determine the charge on each droplet.
- He found that the charge on each droplet was always an integral multiple of the charge on an electron.

Conclusion:

- The quantization of electric charge is a fundamental property of nature.
- It is observed in all known systems, from the smallest subatomic particles to the largest galaxies.
- This property is a consequence of the discrete nature of electric charge, which can exist only as an integer multiple of the charge on an electron or a proton.