Los MODELOS ATÓMICOS: Demócrito, Dalton, Thomson, Rutherford, Bohr, Sommerfeld, Cuántico

Atomic Models: A Historical Overview

Introduction to Atomic Models

• Atomic models are graphical representations of an atom's structure and function, evolving through history as scientific understanding progressed.

• The concept of the atom originated in ancient Greece, initially viewed as a philosophical idea rather than a scientific fact.

Understanding Atoms

• Atoms are submicroscopic structures that constitute all matter, from everyday objects to celestial bodies like stars and galaxies.

• They consist of protons (positive charge), neutrons (no charge), and electrons (negative charge), with protons and neutrons forming the nucleus.

Early Theories: Democritus

• Democritus proposed that all matter is made up of indivisible particles called atoms, which he believed were eternal and indestructible.

• His ideas were largely ignored until modern science revived interest in atomic theory.

The Development of Modern Atomic Models

Dalton's Atomic Model

• John Dalton introduced the first modern atomic model in 1803, asserting that atoms are solid spheres and indivisible.

• He illustrated his theory by creating wooden spheres representing different chemical elements.

Thomson's Discovery of Electrons

• Joseph John Thomson discovered electrons in 1897, demonstrating their negative charge through cathode ray experiments.

• His "raisin pudding" model depicted atoms as positive spheres with electrons embedded within them.

Rutherford's Nuclear Model

• Ernest Rutherford conducted experiments in 1911 that revealed the existence of a small, dense nucleus within the atom after observing alpha particle deflections.

• This model likened the atom to a miniature solar system with electrons orbiting around a positively charged nucleus.

Advancements in Atomic Theory

Bohr's Circular Orbits

• Niels Bohr improved upon Rutherford’s model in 1913 by proposing that electrons occupy stable circular orbits at fixed distances from the nucleus.

Atomic Models and Their Evolution

The Bohr Model and Its Limitations

• The Bohr model explains that when an electron moves to a lower energy orbit, a photon is produced. However, it fails to adequately describe atoms with more than one electron.

Sommerfeld's Atomic Model

• Arnold Sommerfeld expanded the Bohr model in 1916, incorporating Einstein's theory of relativity. He discovered that some electrons orbit the nucleus at speeds approaching the speed of light (300,000 kilometers per second).

• Key modifications made by Sommerfeld include:

• Electrons can move in both circular and elliptical orbits, unlike Bohr’s original circular-only model.

• Within the same energy level, there are sublevels with slightly different energies.

Quantum Mechanical Model

• The quantum mechanical model is currently accepted as the most accurate atomic model. It was developed by three prominent scientists: Werner Heisenberg, Erwin Schrödinger, and Louis de Broglie.

Characteristics of the Quantum Mechanical Model

• This model rejects the notion of electrons orbiting the nucleus in fixed paths. Instead, it introduces electron clouds—regions around the nucleus where an electron may be found.