Early Atomic Models Quiz

Early Atomic Models

• Democritus first named the atom
• Aristotle proposed that atoms were composed of different proportions of air, fire, water, and earth
• Dalton proposed the first model of the atom
• Dalton described atoms as theoretically solid spheres
• Dalton stated atoms of the same element are similar and different elements have different atoms.
• Dalton proposed that atoms combine in specific ratios to form compounds.
• Baker demonstrated that gases conduct electricity under specific conditions.
• Thomson discovered the electron, and proposed the "plum pudding" model of the atom.
• Thomson demonstrated that the properties of electrons do not depend on the electrode or gas.
• Thomson stated the electron is emitted from the cathode and goes to the anode.

Rutherford's Atomic Model and Experiment

• Rutherford's experiment aimed to determine if the atom was solid or not.
• Rutherford proved the existence of a positively charged nucleus, an idea proposed earlier by Thomson but through experimental methodology.
• Rutherford's experiment showed that some alpha particles were deflected due to repulsion from the positive charge of the nucleus
• Rutherford's experiment showed that the results of some alpha particles were deflected and some bounced back, implying the presence of a nucleus.

Bohr's Atomic Model

• Bohr proposed that the atom has a nucleus in the center with electrons orbiting around it.
• Bohr correctly explains the hydrogen spectrum.
• Electrons orbit around the nucleus in fixed energy levels (also called orbits).
• Electrons do not exist between energy levels (orbits)
• Electrons gain energy when moving to a higher energy level and lose energy when moving to a lower energy level.
• Energy changes of electrons are quantized, occurring in discrete amounts.
• Bohr successfully explained the hydrogen atomic spectrum.
• The mass of the nucleus is stable, due to the simultaneous presence of a centrifugal force and the nucleus's attraction to the electron.

Modern Atomic Model

• The uncertainty principle stated that it is impossible to determine both the position and velocity of an electron simultaneously.
• Schrödinger developed the modern wave mechanical model of the atom.
• Schrödinger found that electrons do not orbit the nucleus in fixed paths around the nucleus, but instead in probable distributions of regions of space.
• Schrödinger proposed the concept of electron clouds.
• Different types of orbitals exist at different energy levels.
• Bohr introduced the quantum number (N) to determine the distance between an electron and the nucleus.
• Secondary quantum number (L) decides the number of sub-energy levels within each principal level.
• The magnetic quantum number (mL) describes the spatial shape of the orbitals.
• The spin quantum number (ms) describes the electron’s rotation.