Evolution of Atomic Models and Nuclear Physics Principles

Nuclear Physics

A branch of physics that studies the properties and behavior of atomic nuclei.

Historical Foundations

• Democritus: Formulated the theory that matter consists of indivisible particles called atoms (Greek atomos = indivisible).
• John Dalton: Proposed a new theory on the constitution of matter in 1803.
• Elements: Fundamental units called atoms, honoring Democritus.
• Compounds: Consist of molecules whose structure is formed by the union of atoms in definite and constant proportions.

Subatomic Discoveries

In the late nineteenth century, it was discovered that atoms are not indivisible but are composed of several types of elementary particles.

• Electron: The first particle discovered in 1897.
• Core: Composed of positively charged protons and neutrons, which have no charge.

Evolution of Atomic Models

Joseph John Thomson (1898)

The atomic model takes into account the existence of the electron. It is static, assuming electrons are at rest within the atom and that the core is electronically neutral.

Ernest Rutherford (1911)

Demonstrated the existence of the atomic nucleus. The entire mass of the atom is concentrated in a tiny nucleus with a positive electric charge, while electrons orbit the nucleus in circular paths.

Niels Bohr (1922)

Electrons spin at high speeds around the atomic nucleus in circular orbits that determine different energy levels. By absorbing energy, electrons can move to a higher level; to return to their original level, they must release the absorbed energy. This is the basis of nuclear physics.

Erwin Schrödinger (1926)

Electrons orbit the nucleus but behave like waves moving around the nucleus at certain distances and energy levels. This is considered the most accurate model.

Properties of Light

• Light Source: An object capable of emitting light itself.
• Opaque: A material that does not allow the passage of light.
• Translucent Body: A material that allows the passage of a certain percentage of light.
• Ray of Light: A straight line representing the direction and sense of light propagation.