atom timeline

Demoncritus(part1)

460 BCE

Demoncritus made important discoveries in the spand of his lifetime but overal the most important one was the discovery of the “atom” which in Greek means “invisible”.He called it the invisible because he believed the atom was unbreakable after simple experiments such as breaking a seashell over and over again until he was left with powder,but couldn't break it more. And discovered the building block of life the atom.

Demoncritus(part2)

460 BCE

As he kept powdering he theorized these tiny particles stuck together like Velcro they could fit together but only break at the seams.

John Dalton

1803

Proposed that each chemical element is composed of its own type of atoms that all have the same relative weight.His theory explains why when two fixed weights of substances combine they always form a new compound.He made his theory by using his knowledge of the law of conservation of mass and the law of constant composition.

Eugene Goldstein

1886

In 1886 Eugene Goldstein discovered canal rays(beams of positively charged ions/cations). He discovered the proton with experiments he did with the cathode rays,by attracting them to a positively charged electrode and also knocking electrons of the atoms.He discovered a lot of properties about the cathode rays and later led to the identification of the electron.With Goldstein discovery scientists got a better idea of the structure of a atom and also identifying parts of the protons and atoms.

JJ Tomson

1897

Discovered the electron from measuring the angle where cathode rays were deflected by magnetic fields he was able to decipher the ratio of electric charge to mass. Realizing the e/m was the same for all gases used in the experiment led him to discover whatever particle made the rays were in every kind of gas. Concluding said particle must be a part of the atoms in the gases.

Ernest Rutherford(part1)

1907

Ernest Rutherford known as the father of nuclear physics, proved in his early work that radioactivity involved the nuclear transmission of one chemical element to another, later named alpha and beta radiatio.In 1907 Rutherford used his gold foil experiment to discover the model of the atom he theorized that all positive charges were centralized while negative charges orbited the nucleus.In 1911 although he could not prove the atom as a positive or negative,

Ernest Rutherford(part2)

1907

he theorized the atom has its charge concentrated in a tiny nucleus.Later on in 1917 he conducted research that led to the first splitting of an atom in a reaction between nitrogen and alpha particles and named the proton. Under his leadership the neutron was discovered by James Chadwick in 1932,same year under his directions Rutherfords students split the nucleus in a fully controlled manner.

Robert Millikan

1909

Discovered measurement of electrical charge in electrons.
He sprayed drops of oil into a special chamber and measured how the charges carried by electrons in the drops affected the drops fall.

Niels Bohr

1913

Was a danish physicist,who developed theory about the structure of the atom he proposed that the electrons could travel only in certain larger orbits around the nucleus.He believed the outer orbits could hold more electrons than the inner ones.He also believed the electrons in the outer orbit determined the atom's chemical properties.He developed his theory when he worked with Ernest Rutherford when realized Rutherford’s model had a few problems.

James Chadwick (part1)

1932

James chadwick is remembered for his discovery of the neutron which is referred to as the historical beginning of nuclear physics.Physicists are able to use neutron as a tool to investigate more about atoms.
In the 1930s after series of experiments Joliot-Carie believed the radiation which must be high energy gamma protons was hitting the paraffin target,but Chadwick didn't think this explanation fit because photons have no mass so they wouldn't be able to knock down

James Chadwick(part2)

1932

a heavy particle such as a proton.In 1932 Chadwick began to try similar experiments and got more convinced that the radiation was a neutral particle that has the same mass as an proton was ejected by beryllium.Shortly after 2 weeks of experiments James Chadwick published “The possible existence of a neutron”.A few months later in May Chadwick submitted the more definite paper”The existence of a neutron”.In 1934 the neutron had been established as the new fundamental particle,

James Chadwick(part3)

1932

this changed a lot of scientists view about the atom and Chadwick was awarded the Nobel award in 1935 for his discovery. (Scientists later discovered nuclear weapons )