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lavoisier
in 1783, Lavoisier reacted oxygen with inflammable air, obtaining "water in a very pure state." He correctly concluded that water was not an element but a compound of oxygen and inflammable air, or hydrogen as it is now known. -
john dalton
In 1803 Dalton discovered that oxygen combined with either one or two volumes of nitric oxide in closed vessels over water and this pioneering observation of integral multiple proportions provided important experimental evidence for his incipient atomic ideas. -
newlands law of octaves
the chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical properties occur after each interval of seven elements. -
discovery of radioactivity
Henri Becquerel Discovers Radioactivity. In one of the most well-known accidental discoveries in the history of physics, on an overcast day in March 1896, French physicist Henri Becquerel opened a drawer and discovered spontaneous radioactivity. -
phataelectric effect
photoelectric effect, phenomenon in which electrically charged particles are released from or within a material when it absorbs electromagnetic radiation. The effect is often defined as the ejection of electrons from a metal plate when light falls on it. -
Mendeleev's periodic table
What is Mendeleev's periodic table law?
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What is the law of the Mendeleev periodic table? Mendeleev claimed the famous periodic law that “Element properties are a periodic function of their atomic weight. -
discovery of the electron
During the 1880s and '90s scientists searched cathode rays for the carrier of the electrical properties in matter. Their work culminated in the discovery by English physicist J.J. Thomson of the electron in 1897. -
charge of the electron
Electrons have an electric charge of −1 and their mass is approximately about 1/2000 the mass of a neutron or proton. Electron charge is usually denoted by the symbol e. -
the discovery of the proton
The proton was discovered by Ernest Rutherford in the early 1900's. During this period, his research resulted in a nuclear reaction which led to the first 'splitting' of the atom, where he discovered protons. He named his discovery “protons” based on the Greek word “protos” which means first. -
plato
PLATO (Package for Linear-combination of ATomic Orbitals) is a suite of programs for electronic structure calculations. It receives its name from the choice of basis set (numeric atomic orbitals) used to expand the electronic wavefunctions. -
the alchemists
strange blends of the principles of fire, earth, water and air, and of mercury, sulfur and salt. -
Democritus
Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through empty space until stopped. Differences in atomic shape and size determined the -
plum pudding model
The plum pudding model (also known as Thomson's plum pudding model) is a historical scientific model of the atom. The plum pudding model is defined by electrons surrounded by a volume of positive charge, like negatively-charged “plums” embedded in a positively-charged “pudding” -
plancks quantum theory of light
ight 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. -
rutherfords gold foil experiment
A piece of gold foil was hit with alpha particles, which have a positive charge. Most alpha particles went right through. This showed that the gold atoms were mostly empty space. -
bohrs planetary model
According to the Bohr model, often referred to as a planetary model, 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. -
Robert Millikan
Robert Millikan was a physicist who discovered the elementary charge of an electron using the oil-drop experiment. -
mosley atomic numbers
In 1914 Moseley published a paper in which he concluded that the atomic number is the number of positive charges in the atomic nucleus. He also stated that there were three unknown elements, with atomic numbers 43, 61, and 75, between aluminum and gold. -
Heisenberg uncertainty principle
Formulated by the German physicist and Nobel laureate Werner Heisenberg in 1927, 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; the more we nail down the particle's position, -
discovery of the neutron
in 1932 James Chadwick announced that the core also contained a new uncharged particle, which he called the neutron. Chadwick was born in1891 in Manchester, England. -
schrodinger equation
The Schrödinger equation is a linear partial differential equation that governs the wave function of a quantum-mechanical system -
aristotle
As the father of western logic, Aristotle was the first to develop a formal system for reasoning. He observed that the deductive validity of any argument can be determined by its structure rather than its content, for example, in the syllogism: All men are mortal; Socrates is a man; therefore, Socrates is mortal.