Atomic Theory Timeline by

Origin Of Atomic Theory (2500 Years Ago)

wgdfy9sfs7 — 2023-12-22 02:37:46 UTC

The theory that atoms are the minuscule, indivisible particles that comprise all matter was first proposed by the Greek philosophers Leucippus and Democritus. They claimed that different substances were made up of specific forms of particles.

The Electron (Late 1800s)

wgdfy9sfs7 — 2023-12-22 02:42:06 UTC

Using discharge tubes, physicist J.J. Thompson discovered that negatively charged electrons exist. He concluded that the mass of an electron is approximately 1000 times smaller than that of a hydrogen atom, which put the theory of atomic structure to a test.

The Plum Pudding Model (Late 1800s)

wgdfy9sfs7 — 2023-12-22 02:45:50 UTC

The Plum Pudding Model, brought out by J.J. Thompson, claimed that electrons were dispersed at random within a positively charged structure. This concept aimed to explain why atoms are often neutrally charged.

The Nucleus (1909)

wgdfy9sfs7 — 2023-12-22 02:49:35 UTC

Through experiments with alpha particles on gold foil, physicist Ernest Rutherford developed the model. He concluded that the majority of an atom is made up of empty space, and that atoms have a concentrated positively charged nucleus.

The Proton (Early 20th Century)

wgdfy9sfs7 — 2023-12-22 02:55:41 UTC

Through the alpha particle experiments, Rutherford discovered protons, establishing them as fundamental particles with a positive charge. His discoveries made a substantial contribution to our knowledge of atomic structure.

The Planetary Model (1911)

wgdfy9sfs7 — 2023-12-22 03:02:09 UTC

Led by Rutherford, Neils Bohr theorized the Planetary Model, demonstrating electrons circling a central nucleus. This concept proposed particular electron orbits.

The Quantum Model (1927)

wgdfy9sfs7 — 2023-12-22 03:11:56 UTC

Precise electron position and momentum at the same time were questioned by Werner Heisenberg's uncertainty principle. The result was the creation of the Quantum Model, which claimed that electrons possess properties of both particles and waves. Orbitals are introduced, and electron locations are expressed in terms of probability.