Atomic Theory Project

Chemistry 11

Timeline

Timeline:

Ms. Esma SalihuMade by: Edi Berisha

Atomic theory

Scientists

7. erwin schrödinger

6. sir james chaddwick

5. niels bohr

4. Sir earnest rutherford

3. Sir jj thompson

2. John Dalton

1. Democritus

Scientists

Models

5. rutherford's nuclear model

4. Plum (raisin) pudding

3. Planetary or solar system model

2. Electron cloud model

1. invisible, solid sphere model

main models

Democritus

Democritus thought that atoms were uniform, hard, solid, incompressible, and unbreakable, and that they travelled endlessly across empty space until coming to a stop. The varied qualities of matter were defined by variations in atomic size and form. He created the first atomic model, which is depicted above and is now known as Democritus' Atomic Model.

Democritus' Atomic Model

400 BC

1808

Dalton hypothesised that an atom is a solid sphere that could not be divided into smaller particles. He came up with his theory as a result of his research into gases. His atomic model is shown on the right.

Indivisible, solid sphere model

1766-1844

John Dalton developed a crude method for measuring the masses of the elements in a compound. His law of multiple proportions today is one of the most helpful tools to identify compounds.

John Dalton

1808

1904

The plum pudding model (also known as Thomson's plum pudding model) is a historical scientific model of the atom. The plum pudding model is defined by electrons surrounded by a volume of positive charge, like negatively-charged “plums” embedded in a positively-charged “pudding” (hence the name).

Plum pudding model

1856-1940

On his return from America, he achieved the most brilliant work of his life – an original study of cathode rays culminating in the discovery of the electron, which was announced during the course of his evening lecture to the Royal Institution on Friday, April 30, 1897.

Sir JJ Thompson

1904

1911

Rutherford's model proposed that the negatively charged electrons surround the nucleus of an atom. He also claimed that the electrons surrounding the nucleus revolve around it with very high speed in circular paths. He named these circular paths as orbits.

Rutherford's nuclear model

1871-1937

Rutherford found that nitrogen nuclei ejected what he suspected was "a hydrogen atom" when bombarded with energetic α (alpha) particles. Subsequently, he named this fundamental particle the proton.

Sir Ernest Rutherford

1911

1913

According to the Bohr model, often referred to as a solar system model, the electrons encircle the nucleus of the atom in specific allowable paths called orbits. When the electron is in one of these orbits, its energy is fixed.

Planetary model

1885-1962

Recognition of his work on the structure of atoms came with the award of the Nobel Prize for 1922. Niels Bohr proposed a model of the atom in which the electron was able to occupy only certain orbits around the nucleus.

Neils Bohr

1913

1926

The electron cloud model is a model of an atom in which the atom consists of a small but massive nucleus surrounded by a cloud of rapidly moving electrons.

Electron cloud model

1885-1962

Assuming that matter (e.g., electrons) could be regarded as both particles and waves, in 1926 Erwin Schrödinger formulated a wave equation that accurately calculated the energy levels of electrons in atoms.

Erwin Schrödinger

1926

1932

Sir James Chadwick

In 1932, Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of neutrons – elementary particles devoid of any electrical charge; positively charged protons and neutral neutrons bound together as the atom's nucleus, with negatively charged electrons occupying energy levels surrounding the nucleus.

Chadwicks' Atomic Model

• https://www.britannica.com/biography/James-Chadwick
• https://www.nuclear-power.com/nuclear-power/reactor-physics/atomic-nuclear-physics/fundamental-particles/what-is-electron-properties-of-electron/electron-cloud/#:~:text=The%20electron%20cloud%20model%20is,to%20be%20in%20specific%20areas.
• https://study.com/academy/lesson/james-chadwick-biography-atomic-theory.html#:~:text=Chadwick%20Atomic%20Model,-James%20Chadwick's%20discovery&text=The%20atomic%20model%20after%20Chadwick's,energy%20levels%20surrounding%20the%20nucleus.
• https://www.britannica.com/biography/Erwin-Schrodinger
• https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Introductory_Chemistry_(CK-12)/05%3A_Electrons_in_Atoms/5.06%3A_Bohr's_Atomic_Model#:~:text=According%20to%20the%20Bohr%20model,orbits%2C%20its%20energy%20is%20fixed.
• https://sites.google.com/site/historyoftheaatom/neils-bohr-solar-system-model
• https://byjus.com/chemistry/rutherfords-model-of-atoms-and-its-limitations/#:~:text=Rutherford's%20model%20proposed%20that%20the,these%20circular%20paths%20as%20orbits.
• https://www.toppr.com/ask/question/what-is-the-plum-pudding-model/
• https://www.nobelprize.org/prizes/chemistry/1908/rutherford/biographical/
• https://www.britannica.com/biography/J-J-Thomson
• https://flexbooks.ck12.org/cbook/ck-12-chemistry-flexbook-2.0/section/4.6/primary/lesson/daltons-atomic-theory-chem/
• https://plato.stanford.edu/entries/democritus/

References:

Timeline

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