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427 BCE
plato
hes the first person who had created a school -
384 BCE
aristotle
he invented the field of formal logic and was taught by plato -
400
democritus
Democritus was a central figure in the development of the atomic theory of the universe -
1500
the alchemists
they invented experimental techniques and laboratory tools and also developed practical knowledge about matter as well as sophisticated theories about its hidden nature and transformations. -
lavoisier
he discovered the role of oxygen in combustion and respiration, proved the law of conservation reformed the chemical nomenclature, and named hydrogen. -
john dalton
all matter was comprised of indivisible and indestructible atoms with distinct masses and properties and he introduced the atomic theory to chemistry -
newlands law of octaves
when Elements are put in increasing order of Atomic Mass the qualitys of every eighth Element starting from any Element are a repetition of the properties of the starting Element. -
mendeleevs pd table
presented a new paradigm with all of the elements positioned within a logical matrix -
photoelectric effect
The kinetic energy of photoelectrons increases with light frequency. -
discovery of radioactivity
Marie and Pierre Curie studied the radioactivity of uranium for several years they found out that the elements polonium and radium after chemically extracting uranium from the ore -
discovery of the electron
Scientists found that cathode rays as responsible for the electrical properties in matter. -
charge of electron
In 1897 the elctron was discovered the electron and then went on to propose a model for the structure of the atom -
plancks quantum theory of light
light bulb filaments should be heated to a temperature of about 3,200 Kelvin to make sure that most of the energy is emitted as visible waves -
plum pudding model
name: plum pudding model major finding: they had did experements with cathode ray tubes and it showed that atoms contain tiny negatively charged subtonic particles -
discovery of the protons
Ernest Rutherford research resulted in a reaction which led to the very first splitting of an atom -
robert millikan
he discovered the accurate determination of the charge carried by an electron using the elegant “falling-drop method -
rutherfords gold foil experiment
the atom is mostly empty space with a tiny dense positively-charged nucleus -
bohrs planetary model
the electrons travel around the nucleus of an atom in distinct circular orbits its also referred to as the planetary model of an atom -
mosleys atomic numbers
the atomic number is the number of positive charges in the atomic nucleus He also hadf said that there were three elements nobody knew with atomic numbers 43, 61, and 75, between aluminum and gold -
schrodinger equation
describes the form of the probability waves that govern the motion of small particles -
heisenberg uncertainty principle
there is a fundamental limit to what one can know about a quantum system. -
discovery of the neutron
physicists knew that most of the mass in the atom was located in a nucleus at its center, and that this central core contained protons then they found another particle that had no charge and named it neutron
