Atomic Structure Models and Spectral Analysis

1. Rutherford Model

The Rutherford model describes the atom as follows:

• The atom possesses a nucleus with a small, positive electric charge that contains almost all the mass of the atom.
• Electrons, which have a negative electric charge, orbit the nucleus at small distances in circular paths.
• The total negative electric charge of the electrons must equal the positive charge of the nucleus, ensuring the atom is electrically neutral.

2. Atomic Spectra

A spectrum is the decomposition of wave radiation into its constituent simple waves. When investigating the energy emitted or absorbed, spectra are classified:

Spectrum Types Based on Emission/Absorption:

• Emission Spectrum: Electromagnetic radiation produced directly by a body. It depends on the nature and conditions of the body (e.g., arc spectrum, flame spectrum, thermoluminescence).
• Absorption Spectrum: Shows the energies absorbed by a body or substance.

Classification by Appearance:

• Line Spectrum: The radiation emitted or absorbed corresponds to individual atoms undergoing electronic transitions between two energy levels.
• Band Spectrum: Occurs when atoms combine to form molecules; these spectra are unique to the molecule.
• Continuous Spectrum: Presents the full range of energy within a chosen region. No discontinuities between two wavelengths are observed.

3. Bohr Model

The Bohr model is based on four postulates:

1. Electrons orbit the nucleus in stationary orbits without emitting energy.
2. Orbits are only possible when the electron's angular momentum is an integer multiple of $h/2\pi$. ($mvr = n\frac{h}{2\pi}$)
3. When an electron passes from a higher orbit ($E_2$) to a lower orbit ($E_1$), the energy difference between the two is emitted as electromagnetic radiation. ($E_2 - E_1 = h\nu$)

4. Bohr-Sommerfeld Model

This model attempted to introduce more detail regarding the electron's energy states and transitions. It proposed that:

• The electron could transit between energy states via elliptical orbits, in addition to circular ones.
• It also suggested the existence of several sublevels of slightly different energy within the main orbits.

5. Heisenberg's Uncertainty Principle

According to this principle, it is impossible to simultaneously measure two conjugate variables (like position and momentum) with absolute precision.