Atomic Theory and Structure Quiz

Atomic Theory and Structure

• Dalton's atomic theory: elements are composed of atoms, indivisible and indestructible; atoms of the same element are identical in mass and properties; atoms combine in simple whole number ratios to form compounds.

J.J. Thomson's Experiments

• Discovered the electron: using cathode ray tubes, observed deflected rays, concluding negatively charged particles (electrons) exist within atoms.

• Plum Pudding Model: atoms consist of a diffuse sphere of positive charge with electrons embedded randomly within it, like raisins in a pudding.

Radioactivity

• Spontaneous disintegration of an atomic nucleus.
• Discovered by Becquerel and Marie Curie.
• Rutherford's experiments involved gold foil and alpha particles, leading to the discovery of a positively charged nucleus.

Atomic Model Developments

• Rutherford: Proposed a nuclear model with a dense, positively charged nucleus containing most of the atom's mass, with electrons orbiting around it.

Isotopes

• Atoms of the same element with differing numbers of neutrons.
• Same atomic number (number of protons) but different mass numbers (protons + neutrons), and thus different masses.

Radioisotopes

• Isotopes with unstable nuclei, releasing energy and/or particles.
• Examples: Radioactive decay, emitting gamma rays and subatomic particles.

Light and Electromagnetic Radiation

• Light is a form of electromagnetic radiation.
• Different wavelengths correspond to different colours (visible light is part of the electromagnetic spectrum).

Planck's Quantum Theory

• Energy is quantized, meaning it exists in discrete packets or quanta.
• Planck's constant (h) relates energy (E) and frequency (f) of radiation (E=hf).

Photoelectric Effect

• Emission of electrons when light shines on a material.
• The energy of the emitted electrons depends on the frequency of the incident light, not the intensity.

Einstein's Theory of Light as Particles (Photons)

• Light consists of discrete packets of energy called photons.
• Photons transfer energy to electrons, enabling them to escape from matter.

Bohr Model of the Atom

• Electrons orbit the nucleus in specific energy levels or shells.
• Electrons can jump between energy levels by absorbing or emitting energy in the form of quanta, thus explaining line spectra

Quantum Mechanics

• Electrons' precise position and momentum cannot be known simultaneously (Heisenberg's Uncertainty Principle).
• Orbitals represent probability distributions for finding electrons in specific regions around the nucleus.

Quantum Numbers

• Set of numbers describing an electron's properties within an atom (n, l, ml, ms).
• Principal Quantum Number (n): energy level and size of the electron cloud/orbital.
• Angular Momentum Quantum Number (l): shape of the electron cloud (orbital) (s, p, d, or f).
• Magnetic Quantum Number (ml): orientation of the electron cloud in space.
• Spin Quantum Number (ms): direction of the electron spin (+1/2 or -1/2).

Pauli Exclusion Principle

• No two electrons in an atom can have the same set of four quantum numbers.
• This principle dictates electron arrangements in atoms.