Key Figures in Atomic Theory and Chemistry
John Dalton
British physicist and chemist
His studies included meteorological observations.
Origin of instruments for rain and weather measurements.
1. Large measure of weather phenomena.
What was Dalton’s first work? Observations and tests in 1773.
Key theory: Elements and compounds.
His theory consisted of the atomic nature of elements and compounds: Material formed by atoms.
Atoms of different masses combine in simple ratios to form compounds.
How did the atomic theory emerge? Through the study of the physical properties of atmospheric air and other gases.
Dalton’s structure drawing: CO2
Joseph Thomson
Describe the atomic model: Atoms with electrons embedded.
– Charge at atom + like raisins in a pudding.
What are cathode rays? Electrons produced between metal terminals in evacuated gas tubes.
What are corpuscles? Properties of particles with mass and movement (DCIR).
What is an isotope? Identical chemical substances with atoms of different masses.
What does DCIR rely on for atoms? Atoms are divisible: matter is composed of small particles.
Three discoveries by Thomson: Cathode rays, mass spectrometer, and electron isotopes.
Why is he called the father of electrons? He was the first to discover the subatomic particle and develop an atomic model known as the raisin cake model.
What experiment did Thomson do to receive the Nobel Prize in Physics in 1906? He showed that the atom was composed of negatively charged electrons in a positively charged pudding, with electrons distributed uniformly.
Electron: Basic particle with a negative charge.
Conclusion of the first experiment: Negative charge is inseparable from the ray.
Conclusion of the second experiment: Cathode rays could bend under the influence of an electric field.
Conclusion of the third experiment: The atomic model was like a raisin pudding, a sphere with positive charge and electrons embedded, resulting in a neutral atom.
Ernest Rutherford
New Zealand
What experiment did he do to classify types of radiation? Located uranium between two plates, measuring current, and concluding that alpha and beta radiation existed.
Why did he win the Nobel Prize? In 1908, for his work on radioactivity and the disintegration of elements.
What happens when radiation interacts with air? It ionizes the air.
He identified radiation types: alpha, beta, and gamma.
What was Rutherford’s atomic model? There is a central core called the nucleus.
Why is he considered the father of nuclear physics? He established the existence of the subatomic nucleus, forming the basis of nuclear physics.
Why is he seen as an alchemist? He achieved artificial transmutation, changing the nature of nitrogen into oxygen.
Niels Bohr
Danish physicist, Nobel Prize 1922
What was his atomic model based on? Rutherford’s atomic model, using quantum theory and Planck’s constant.
What were the errors in Bohr’s atomic model? It did not account for the splitting of spectral lines observed in high-power spectroscopes, and the atom was assumed to be planar.
Why work with the hydrogen atom? Because it is light.
What does it mean when an electron is excited? When electrons jump to higher energy levels by absorbing energy.
What does Bohr propose in his atomic model? Electrons move in circular orbits around the nucleus at fixed energy levels. Electrons do not emit or absorb energy while in these orbits, only when transitioning between them.
Max Planck
German, Nobel Prize 1918, Creator of Quantum Theory
Most important contribution: Quantum Theory.
What are quanta? Minimum expression of energy in packets.
Where did quantum theory originate? From experiments on black body radiation.
What are the postulates of quantum theory? Radiant energy is discontinuous, consisting of small particles called quanta.
What does Planck’s law state? Quantum energy is the frequency of radiation multiplied by a universal constant.
Albert Einstein
German, Father of Physics
What experiment did Einstein do to win the Nobel Prize? The photoelectric effect.
What is the photoelectric effect? The process by which electrons are released from a material by radiation. A photon is fully absorbed by an electron.
Characteristics of the theory of relativity: Describes physics under flat spacetime for constant velocity. It also proposes that spacetime is not affected by the presence of matter.
Why is the theory of relativity important in Einstein’s life? It made him a renowned scientist.
Why is Einstein called the father of physics? His ideas made quantum mechanics possible.
Photoelectric effect: Photons.
What type of speed is used to explain the theory of relativity? Constant speed.
Paul Dirac
British, Nobel Prize 1933
What did he contribute to atomic theory? He developed equations that included relativistic theory and explained electron behavior.
What property of the electron did he explain? The property of spin, which could be + or – at high speeds, and its response to the electromagnetic spectrum, with a numeric value of +1/2 or -1/2.
What problem arose in solving the equation? What solution did he give? The equation required the existence of a positively charged “anti-electron” (positron). He proposed the existence of antimatter.
What is an anti-electron? Antiparticles with the same characteristics, except for the opposite charge.
Why did Dirac deny the existence of an anti-electron? He concluded that they would annihilate each other, which was inconceivable at the time. Later, Anderson confirmed the existence of the positron.
Erwin Schrödinger
Austrian physicist, Nobel Prize 1933
What were his contributions to physics? He created the Schrödinger equation and wave mechanics.
Why did he receive the Nobel Prize? For formulating the equation that bears his name.
What does the equation explain? It indicates how a physical state changes over time.
What does Schrödinger’s paradox explain? Neither classical nor quantum mechanics fully explain natural phenomena.
What was Schrödinger’s contribution to chemistry? The atomic model, establishing quantum numbers and sublevels.
What is Schrödinger’s wave mechanics? A mathematical set describing the behavior of electrons and atoms.
What does Schrödinger’s atomic model explain? It describes the electronic structure of the atom and its interaction with other atoms.
What conditions must be met for the equation to be valid? There should be no contribution from lost particles or energy, and the rest energy should not be comparable to kinetic energy.
What are the features of an isolated system? It cannot interact with the atmosphere, so there is no energy or mass transfer.
Where is it most probable to find an electron? Closest to the nucleus.
Louis de Broglie
French, Nobel Prize 1929, Duality
Why did he receive the Nobel Prize? For his theory of wave-particle duality.
What requirements must an element meet to be considered a particle? It must have mass, energy, and time (speed and position).
What requirements must an element meet to be considered a wave phenomenon? It must possess wave properties.
What are the properties of waves?
- Refraction: The wave deviates when it meets a different medium.
- Reflection: The wave bounces off a medium, and part of it is inverted.
- Diffraction: The bending of waves when encountering an obstacle.
Why does the electron have wavelike characteristics? Because it moves within the atom as both a wave and a particle.
What are the characteristics of a particle? It has mass and position in time.
What did Broglie postulate? That the electron had dual properties, later generalized to all matter.
How is Broglie’s contribution applied to chemistry? The creation of the Schrödinger atomic model, considering the orbitals of atoms to explain this duality.
Who performed the experimental verification of the wave characteristics of the electron? Davisson and Germer, who showed that electrons undergo diffraction.
Who proposed the current atomic model? Schrödinger.
What are atomic orbitals? The area of greatest probability of finding an electron in an atom.
Antoine Lavoisier
Chemist, Paris, Father of Modern Chemistry
Why is he considered the father of modern chemistry? For his studies on oxidation, animal respiration, air analysis, and the conservation of mass.
What is the theory of phlogiston? A substance released during burning, which stops when the ashes are formed.
Why did Lavoisier question the theory of phlogiston? Because rusted metal had a greater mass than the original metal.
How did Lavoisier solve the problem of measuring gases? Using hermetically sealed containers.
What was the procedure in his experiment? He measured the mass of an airtight container with a solid substance inside, heated it, and then measured the mass again.
What results were obtained in the experiment? The mass remained constant, including the gases released during combustion.
What is the basis for proposing the law of conservation of mass? His experiments on combustion and oxidation.
What is the fundamental principle of the law of conservation of mass? Matter is neither created nor destroyed, only transformed from one form to another.
How does the law of conservation of mass relate to combustion? It verifies Lavoisier’s theory, as gases are included in the process, which had not been considered before.
Marie Curie
Polish, Nobel Prize in different fields
Explain her contribution to the scientific community: She discovered two new radioactive elements, polonium and radium. She pioneered the use of radioactivity in medicine and contributed to the work of H. Becquerel on radioactivity.
Are her contributions relevant? Yes, because her studies in radioactivity are used in medicine today.
What is the relationship between her death and her studies on radioactivity? She died due to high exposure to radioactive materials without taking safety measures.
Explain each of her Nobel Prizes: She received the Nobel Prize in Physics in 1903 for her investigations with Becquerel on radiation phenomena, and the Nobel Prize in Chemistry in 1911 for the discovery of radium and polonium and studies on these elements.
Nobel Prize in Chemistry 2008
Who were awarded the ultimate prize? Osamu Shimomura.
What do the acronyms GFP mean? Green fluorescent protein.
What was the name of the jellyfish where it was found? Aequorea.
What is the importance of this discovery? It is used as a light marker to display cell processes, such as cancer and protein behavior.
What is the use of fluorescent proteins for studying chemical processes in live or dead cells? GFP can bind to proteins in any living organism.
Who expanded the range of colors of proteins? Roger Y. Tsien and colleagues, producing various shades covering the rainbow, which allows for the simultaneous study of different proteins in a cell.
What biologist contributed to the sequence of amino acids?
Who was not recognized in the Nobel Prize in Chemistry? Douglas.
Who received the last Nobel Prize in Chemistry?