Discovery of Sub-atomic Particles and Atomic Models

Michael Faraday's Contribution

Electricity passing through an electrolyte leads to chemical reactions at the electrodes, indicating a particulate nature of electricity.

Cathode Ray Experiment

Conducted experiments in cathode ray tubes showing streams of particles (electrons) emitted from the cathode.

Observations of Cathode Rays

1. Not visible but detected by phosphorescent materials. 2. Travel in straight lines in absence of fields. 3. Negatively charged particles.

J.J. Thomson (1897)

Measured the charge-to-mass ratio of electrons resulting in the value \frac{e}{m_e} = 1.758820 \times 10^{11} \text{ C kg}^{-1}.

Robert Millikan's Oil Drop Experiment

Determined the charge of the electron as -1.6 \times 10^{-19} C and the mass as 9.1094 \times 10^{-31} kg.

Canal Rays

Discovered while experimenting with cathode ray tubes, showing the existence of positively charged particles (protons).

Chadwick (1932)

Proposed neutrons found by bombarding beryllium.

John Dalton (1808)

Proposed atomic theory considering atoms as indivisible.

Thomson's Model (1898)

Proposed the 'Plum Pudding' model where electrons were embedded in a positive sphere.

Rutherford's Model (1911)

Discovered through alpha particle scattering that most of the atom is empty with mass concentrated in a small nucleus.

Bohr's Model of the Atom (1913)

Proposed electrons move in defined orbits around the nucleus with quantized energy levels.

Wave-Particle Duality

Developed by Schrödinger, it incorporates wave properties of particles.

Pauli Exclusion Principle

No two electrons can have the same set of quantum numbers.

Hund’s Rule

Every orbital in a subshell gets one electron before any gets two.

Aufbau Principle

Electrons fill orbitals starting from the lowest energy level upwards.

Uncertainty Principle

Position and momentum cannot be precisely measured simultaneously.

Atomic Orbitals

Defined by a set of three quantum numbers and have specific shapes (s, p, d, f).

Quantum Mechanical Model

Refines the understanding of atomic structure with quantized energy levels and probabilistic electron locations.