Understanding Electromagnetic Radiation and Atomic Structure
Electromagnetic Radiation and Atomic Structure
Electromagnetic radiation: E-space propagation involves magnetic and electric waves.
Electric No-Load Movement: Creates magnetic and electric fields.
The nature of electromagnetic radiation is twofold:
- Corpuscular: Emission of small corpuscles or particles (Newton).
- Wave: Wave-type disturbance (Maxwell). Light has a dual nature: wave-particle.
Experimental facts that determine the structure of the atom: The experience of electrical discharges in vacuum tubes, the discovery of radioactivity, and atomic spectra. The study of these phenomena allows us to: discover fundamental particles of the atom, the structure of the nucleus, and the distribution of electrons in the atom.
Planck’s Theory
Planck’s theory supports the dual nature of light. Energy is emitted in discrete packets, only available in specific quantities. This energy is quantized, meaning it exists in multiples of a basic unit. The energy of radiation emitted by a body is given by the expression E = hv (where ‘h’ is a constant and ‘v’ is frequency).
Bohr’s Model
Bohr explained the spectrum of the hydrogen atom by applying Planck’s quantum theory to Rutherford’s atomic model. He proposed three postulates:
- First Postulate: The hydrogen atom has a single proton and electrons describe learning routes around the nucleus without spending energy.
- Second Postulate: Introduction of quantum theory imposed on his model that only certain orbits are possible. The angular momentum (L) is a multiple of h/2π. This allows us to obtain the radii of permitted orbits (for n=1, we have the smallest orbit, corresponding to the lowest energy).
- Third Postulate: Explanation of the hydrogen spectrum: An electron falling from one orbit to another emits a photon (whose frequency is given by Planck’s equation).
Bugs in Bohr’s Theory: Difficulties emerged even with the spectrum of molecules. Sommerfeld perfected the Bohr model by considering that orbits could be elliptical. However, it was not valid for polyatomic atoms because Bohr’s postulates were a mix of classical and quantum mechanics.
The Principle of Wave-Particle Duality
Planck and Einstein supported the wave nature of light, suggesting it behaves as if made of particles (photons). Later, Louis de Broglie suggested that particles could exhibit wave properties. He showed that the wavelength (λ) associated with a particle of mass ‘m’ moving at a speed ‘v’ is given by the equation: λ = h/mv. It was possible to demonstrate the quantum number ‘n’ of Bohr’s theory naturally. It appears that an electronic orbit is stationary (has the same height at a given point) when the length of the orbit is an integer multiple of the electronic wavelength. This leads to the condition imposed by Bohr.
The Mechano-Wave Model
The quantum mechanical model is based on the development of quantum mechanics and uses the Schrödinger wave equation to describe the behavior of small particles such as electrons.
Wave functions measure the probability of finding an electron in a specific location.