Annabella B.2

Plato

427 BCE

That atoms broke down into geometric shapes all forms of triangles and all different cubic shapes based on the elements like air is a octahedron and earth is a tetrahedron

Democritus

400 BCE

Democritus believed that atoms were uniform, incompressible, and that they moved in infinite numbers through empty space until stopped. Democritus thought that a point would be reached at which the cheese couldn't be cut into smaller and smaller pieces. He called these pieces Atomos, which means uncuttable in Greek.

Aristotle

384 BCE

Aristotle not believe in atoms making up matter but her did believe in the elements earth, water, air, fire, and ether making up everything together just like today we believe atoms make up everything.

Alchemists

700

The alchemists believed that all metals were formed from two elements mercury and sulfur. they went on to be the first to isolate famous metals we still use today such as antimony, arsenic and zinc.

Antoine Lavoisier

1783

Antoine Lavoisier Believed that matter was not created or destroyed but later found and proved through an experiment that water was just a compound of inflammable air and hydrogen as now known disproving the phlogiston theory.

John Dalton

1808

John Dalton believed that all matter was a made up of invisible atoms. He went on to say that all Atoms atoms differ in size and shape and that atoms can not be subdivided.

J.A.R. Newlands

Feb 7, 1863

J.A.R Newlands found that arranging the periodic elements in increasing order every seven elements have similar chemical and physical property's. EXP: Lithium and sodium are 7 intervals apart and they have the same valance of electron.

Dmitri Mendeleev

1869

Mendeleev not only created the periodic table he predicted elements to come and left spaces for them even though now we use a periodic table sorted by atomic number Mendeleev's periodic was the first of his time and one of the coolest discovery's in my opinion

Henri Becquerel

Mar 1, 1896

Henri Becquerel accidently found spontaneous radioactivity by placing uranium salts on top of a photographic plate wrapped in black paper. The salts caused a blackening of the plate despite the paper in between. He then went on to do research that effects medicine even in our day.

JJ Thomson

Apr 30, 1897

JJ Thomson found electrons by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged and studied positively charged particles in neon gas.

Max Planck

1900

Max Planck found 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 as he worked in thermodynamics that led to the quantum theory. he was very tedious and timed all day trying his best to collect as much evidence before he could propose his idea

JJ Thomson

1904

JJ Thomson depicted the electrons as negatively-charged particles embedded in a sea of positive charge showing that the atom has a perfectly balanced medium using a comparison like evenly made blueberry muffin

Albert Einstein

1905

Albert Einstein found electrically charged particles are released from or within a material when it absorbs electromagnetic radiation. basically if a million people were walking a tightrope made of metal some would fall off and when they did it would create light that but with electrons

Robert Millikan PT II

1909

Going into further detail he used negatively charged oil droplets and looked in a microscope finding out that the drops lined up in a specific way depending on how many there were

Henry Moseley

1913

Henry Moseley measured the x ray spectra of many elements using the using the diffraction in crystals. this led to him finding 4 missing elements we now know today as technetium, promethium, hafnium and rhenium.

Ernest Rutherford

Dec 8, 1919

his scintillation detectors detected hydrogen nuclei when a beam of alpha particles was shot into the air. alpha particles were observed to scatter backwards from a gold foil Rutherford's explanation, was that the scattering was caused by a dense core at the center of the atom–the nucleus. From then on his research led to one of the first splitting's of an atom where he discovered the proton and named them after the Greek word “protos”

Robert Andrews Millikan

Apr 22, 1923

Robert Millikan founded the accurate charge of and electron using a falling drop method. this showed that electrons had mass and he was able to figure out the exact charge of a singular electron.

Werner Heisenberg

Feb 23, 1927

Heisenberg’s principle states that more precisely we measure the position of a particle, less precisely you can know its velocity and vice versa. It also states that the product of uncertainty in measurement of velocity and uncertainty in measurement of position.

Erwin Schrödinger

1929

Erwin Schrödinger helped them to detect where the electron could be at any given moment. Schrödinger with his head strength mathematical equations to describe the likelihood of finding an electron in a certain position.

James Chadwick

1932

James Chadwick bombarded Beryllium (a light element) with alpha particles from the natural radioactive decay of Polonium. The resulting radiation showed high penetration through a lead shield, which could not be explained via the particles known at that time so he went on to research further and then found a theory that proposed a neutral piece was in the nucleus.

Niels Bohr

Jan 26, 1939

Niels Bohr created a science model for the atom that we still use today showing the electrons outer ring and the neutrons and protons held tightly together in the nucleus. Niels Bohr also helped in creating the atomic bomb later on.

Ernest Rutherford

1991

Ernest Rutherford studied the absorption of radioactivity by thin sheets of metal foil he founded alpha radiation, which is absorbed by a few thousandths of a centimeter of metal foil, and beta radiation, which can pass through 100 times as much foil before it was absorbed. this showed that the atom is mostly empty space with a tiny, dense, positively-charged nucleus.