Atomic Model Development

Year 12 HSC Physics

Plum Pudding Model

An early atomic model proposed by Thomson, depicting atoms as a uniform sphere of positive charge with embedded electrons.

Rutherford Model

An atomic model that introduced a nucleus, showing that electrons orbit around a dense, positively charged center. Nucleus was discovered through the Geiger-Marsden Experiment

Limitation of Rutherford Model

Electrons in circular orbits should emit electromagnetic radiation, lose energy, and spiral into the nucleus, which contradicts observed stability.

Bohr's Model

An improved atomic model that explained emission spectra and incorporated Planck’s quantum hypothesis.

Limitations of Bohr's Model

Inability to predict spectral lines for multi-electron atoms and reliance on a mix of classical and quantum physics.

Emission Spectra

The spectrum of light emitted by elements, consisting of discrete lines corresponding to specific energy transitions of electrons.

Balmer Equation

A formula that describes the wavelengths of the visible spectrum emitted by hydrogen.

Stable Orbits

Specific orbits where electrons can exist without radiating energy, as proposed by Bohr.

Quantized Angular Momentum

The principle that the angular momentum of an electron in a stable orbit is a whole number multiple of $\frac{h}{2\pi}$.

Energy Level Transitions

The process by which electrons move between stable orbits by absorbing or emitting energy, with frequency determined by (E=hf).

Relative Intensity of Spectral Lines

Variation in brightness of spectral lines, indicating differing probabilities of electron transitions.

Hyperfine Spectral Lines

Closely spaced lines in a spectrum, indicating more complex transitions than single lines.

Zeeman Effect

The splitting of spectral lines in a magnetic field, demonstrating the interaction between magnetic fields and atomic energy levels.

de Broglie's Hypothesis

The proposal that electrons exhibit wave properties, altering the understanding of their behavior.

Schrödinger's Contribution

The development of quantum mechanics, fundamentally changing the understanding of electrons and atomic structure.

Wave-Particle Duality

The concept that light and particles exhibit both wave-like and particle-like properties, as shown by Einstein and Planck.

De Broglie Wavelength

The wavelength associated with a particle, significant for atomic objects but negligible for larger objects.

Standing Wave Condition

The idea that stable electron orbits correspond to wave patterns that form standing waves, leading to quantized orbits.

Agreement with Bohr

De Broglie's calculations of stable orbit radii in hydrogen matched those predicted by Bohr's model.