Modelos Atómicos. Cronológicamente. Explicación Completa, Fácil y Sencilla. Resumen.
History of Atomic Models
Introduction to Atomic Theory
- The video introduces the evolution of atomic models and how our understanding of matter has changed over time.
- It begins with ancient Greece, highlighting Democritus, who proposed that matter is composed of indivisible atoms, a concept he believed was eternal and immutable.
Early Philosophical Perspectives
- Other Greek philosophers like Leucippus and Lucretius supported atomic theory; however, Aristotle disagreed, advocating for a model based on four elements: fire, water, air, and earth.
- Aristotle's view dominated for centuries until the 19th century when John Dalton revived atomic theory with a scientific approach.
John Dalton's Atomic Theory
- Dalton's theory posited that matter consists of indivisible particles called atoms. Each element has identical atoms with unique properties.
- He stated that different elements have distinct masses and properties; atoms can combine to form compounds.
Advancements in Atomic Understanding
- Despite its strengths, Dalton’s model could not explain certain electrical phenomena observed later. This led to modifications by J.J. Thomson in 1904.
J.J. Thomson's Model
- Thomson conducted experiments using cathode ray tubes and discovered electrons—negatively charged particles embedded in a positively charged "fluid."
- His model depicted an atom as neutral due to the balance between positive fluid and negative electrons.
Rutherford's Nuclear Model
- In 1911, Ernest Rutherford bombarded gold foil with alpha particles and concluded that an atom consists of a dense nucleus containing protons surrounded by orbiting electrons.
- He emphasized that most of an atom is empty space since the nucleus contains nearly all its mass while electrons occupy much larger orbits.
Niels Bohr's Planetary Model
- Niels Bohr introduced his planetary model in 1913, suggesting electrons exist in defined energy levels around the nucleus without radiating energy.
Evolution of Atomic Models
The Bohr Model and Its Limitations
- The initial atomic model, based on absorption and emission, was effective only for the hydrogen atom.
- Arnold Sommerfeld modified the Bohr model in 1916, introducing elliptical orbits for electrons alongside circular ones.
Sommerfeld's Contributions
- From the second energy level onward, Sommerfeld proposed multiple sublevels within a single energy level.
- He described electrons as tiny electric currents, marking a shift towards relativistic atomic models.
Schrödinger's Quantum Wave Model
- In 1926, Schrödinger introduced the quantum wave model where electrons do not have defined positions but are described by a mathematical function called the wave function.
- Electrons occupy orbitals—regions with high probabilities of finding an electron—rather than fixed orbits.
Discovery of Neutrons
- James Chadwick discovered neutrons in 1932, revealing that atomic nuclei contain both protons and neutrons for stability.
Current Atomic Model: Quantum Mechanical Model
- Today's atomic model is known as the quantum mechanical model, which explains various observed phenomena effectively.
- Significant contributions to this model were made during Solvay Conferences starting in 1911, gathering prominent scientists to discuss advancements in physics and chemistry.