atomic model timeline

Plato

500 BCE

Solid forms of matter are composed of indivisible elements shaped like triangles. Proposed that matter was continuous, infinite, present in every form, and always all around us. It was thought that matter could be divided and subdivided into smaller and smaller pieces without limit. This concept was called the continuous theory of matter.

Democritus

400 BCE

Atoms move in infinite numbers till empty space stopped.He stated that atoms
are indestructible and unchangeable. Also that
they are homogenous, meaning they have no
internal structure. His atomic model was solid,
and stated all atoms differ in size, shape, mass,
position and arrangement, with a void exists
between them.

The Alchemist

760

All metals were formed of sulfur and mercury in various proportions and that altering those proportions could transform the metal under study—even to produce silver or gold from lead or iron.

Solar System Model

1543

The “solar system” model represents an atom as a massive positive body which is the nucleus (like the sun in the solar system) with negative entities which are the electrons (like the planets in the solar system) orbiting around it.

Robert Boyle

1662

the pressure of a given quantity of gas varies inversely with its volume at constant temperature, everything composed of tiny particles

Antone Lavoisier

1789

Grouped elements as substances gasses, metals, physical and chemical. Through a series of experiments found that the total mass of products and reactants in a chemical reactions is always the same.

John Dalton

1803

Dalton's atomic theory proposed that
all matter was composed of atoms,
indivisible and indestructible building
blocks. While all atoms of an element were
identical, different elements had atoms of
differing size and mass.

Billiard Ball Model

1803

He defined an atom to be a ball-like structure, as the concepts of atomic nucleus and electrons were unknown at the time.

Amedeo Avogadro

1811

Equal volumes of gasses at the same temperature and pressure contain the same number of molecules.

Dmitri Mendeleev

1869

Elements are arranged according to the value of the atomic weights present. Mendeleev discovered what is called the Periodic Law. When Mendeleev arranged the elements in order of increasing atomic mass, the properties where repeated.Mendeleev's law allowed him to build up a systematic table of all the 70 elements then known.

JJ Thompson

1896

Atoms contain tiny negatively charged subatomic particles electrons. J. J. Thomson, who discovered the
electron in 1897, proposed the plum
pudding model of the atom in 1904 before
the discovery of the atomic nucleus in
order to include the electron in the atomic
model. In Thomson's model, the atom is
composed of electrons which Thomson still called "corpuscles."

Pierre and Marie Curie

1898

Powerful rays or energy the polonium and radium gave off were tiny atoms that disintegrating inside elements.

Plum Pudding Model

1904

Thomson's atomic model, an atom resembles a sphere of positive charge with electrons (negatively charged particles) present inside the sphere.

Albert Einstein

1905

any liquid is made up of molecules, formulated equation e=mc^2

Robert Millikan

1909

Electrons did have discrete quantifiable charge, and he measured the charge with oil.Thomson had also already calculated the charge-to-mass ratio of an electron, so once Millikan was able to measure the elementary charge, the mass of an electron could also be calculated.

Ernest Rutherford

1911

Described the atom as having tiny, dense, positive and chemical change with the core called nucleus. most of the atom is empty space.

Henry G.J. Mosely

1911

Atomic numbers are the fundamental feature that describes an element. He found that the dilemmas of placing isotopes, same elements having different mass, and the wrong order of elements disappeared.

Neils Bohr

1913

electrons do not radiate energy as they orbit the nucleus, but exist in states of constant energy that's called stationary states

Electron Cloud Model

1926

It showed were more likely electron will be in location. Electrons do not have a fixed orbit, but occur more frequently in certain areas around the nucleus at any given point in time,

Ermin Schrodinger

1926

Studied the behavior of electrons within atoms could be explained by treating them mathematically as matter waves. Discoverer of quantum mechanics

James Chadwich

1932

Discovered neutron in a atom.James Chadwick discovered a third type of sub atomic particle, which he
named the neutron.Neutrons help to reduce the repulsion
between protons and stabilize the atoms nucleus.