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Plato introduced the atomic theory in which ideal geometric forms serve as atoms, according to which atoms broke down mathematically into triangles. -
Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through empty space until stopped. -
In Aristotle's time, atomists held that matter was fundamentally constructed out of atoms. -
Lavoisier believed that matter was neither created nor destroyed in chemical reactions -
The alchemists believed that all metals were formed from two principles — mercury and sulfur. -
All matter is composed of extremely small particles called atoms. -
Newland's law of octaves states when elements are in increasing order of atomic mass every eighth starting from any Element are a repetition of the properties of the starting Element. -
Mendeleev placed elements in the order of their atomic weights in the form of a table known as the Periodic Table of Mendeleev. -
A phenomenon in which electrically charged particles are released from a material when it absorbs electromagnetic radiation. -
On an overcast day French physicist Henri Becquerel opened a drawer discovered spontaneous radioactivity. -
In the 1880s and ’90s scientists searched cathode rays for the carrier of the electrical properties in matter. Their work culminated in the discovery of the electron in 1897 by English physicist J.J Thomson. -
Plank's Quantum theory of light its that light bulb filaments should be heated to a temperature of about 3,200 Kelvin to ensure that most of the energy is emitted as visible waves. -
J.J. Thomson suggested the plum pudding model of the atom. This model had negatively-charged electrons embedded within a positively-charged "soup." -
Gold foil was hit with alpha particles, that are positively charged. Most alpha particles went right through. Showing gold atoms were mostly empty space. -
accurate determination of the charge carried by an electron, using the elegant “falling-drop method” -
The electrons encircle the nucleus of the atom in specific allowable paths called orbits. When the electron is in one of these orbits, its energy is fixed. -
Moseley published a paper in which he stated that the atomic number is the number of positive charges in the atomic nucleus. -
The proton was discovered by Earnest Rutherford. His research resulted to a nuclear reaction which led to the first splitting of the atom where protons were discovered. -
electron, lightest stable subatomic particle known. It carries a negative charge of 1.602176634 × 10−19 coulomb, which is considered the basic unit of electric charge. -
The Schrodinger is a linear partial differential equation that governs the wave function of a quantum-mechanical system. -
The uncertainty principle states that we cannot know both the position and speed of a particle. such as a photon or electron, with perfect accuracy. -
James Chadwick announced that the core of an atom also contained a new uncharged particle, which he called the neutron.