Atomic structure - discovery timeline

© www.teachitscience.co.uk 2016 26554 Page 1 of 4

Date Name Discovery/development

400 B.C.

Democritus

Proposed that all matter is made of

indestructible particles he called atoms.

1789

Antoine Lavoisier

Listed 92 different types of matter which

we know today as 'elements'.

1803

John Dalton

Said that elements consist of identical

atoms and different elements combine to

make compounds.

1869

Dmitri Mendeleev

Created the Periodic Table.

1898

JJ Thomson

Discovered the electron and developed the plum-pudding model of the atom.

Atomic structure - discovery timeline

© www.teachitscience.co.uk 2016 26554 Page 2 of 4

1900

Frederick Soddy

Coined the term 'isotope'.

1908

Robert Millikan

Found out the charge of the electron.

1909

Ernest Rutherford

Demonstrated the existence of the atomic nucleus.

1919

Rutherford and others

Discovered the proton.

1922

Niels Bohr

Proposed the outer shell held more electrons than the inner shell.

Atomic structure - discovery timeline

© www.teachitscience.co.uk 2016 26554 Page 3 of 4

1932

James Chadwick

Discovered neutrons.

1964

Murray Gell-Mann and George Zweig

Suggested elementary particles or ‘quarks’ that make up protons and neutrons.

2015

Large Hadron Collider

Discovery of a new class of particles ‘pentaquarks’.

Atomic structure - discovery timeline

© www.teachitscience.co.uk 2016 26554 Page 4 of 4

Teaching notes

The timeline can be used in a variety of ways – some suggestions below:

Cut up the table for students to construct the timeline. Set up a timeline out of

string and each century marked along it and ask students to peg each event in the

correct place. This will give an idea of the length of time over which our

understanding of atomic structure has developed.

Ask students why it is only in the last century that our understanding of atomic

structure has really developed?

Ask students to write a letter to Democritus that describes the current model for

atomic structure.

Further activities with more information about sub atomic particles can be found at -

particleadventure.org/index.html.

Image credits

1. Democritus / Credit: Wellcome Trust Library \ UIG / Copyright © Wellcome Trust Library / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

2. Antoine Lavoisier / Credit: FPG / Archive Photos / Getty Images / Universal Images Group / Copyright © Getty Images / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

3. John Dalton, English chemist and meteorologist / Credit: SHEILA TERRY / SCIENCE PHOTO LIBRARY / Universal Images Group / Copyright © Science Photo Library / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

4. Dmitri Mendeleev / Credit: Science Source / Photo Researchers / Universal Images Group / Copyright © Photo Researchers / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

5. JJ (Joseph John) Thomson (1856-1940) British physicist / Credit: Universal History Archive/Universal Images Group / Copyright © Universal Images Group / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

6. Frederick Soddy, British radiochemist / Credit: LIBRARY OF CONGRESS / SCIENCE PHOTO LIBRARY / Universal Images Group / Copyright © Science Photo Library / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

7. Robert Millikan / Credit: Science Source / Photo Researchers / Universal Images Group / Copyright © Photo Researchers / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

8. Ernest Rutherford / Credit: Superstock / Universal Images Group / Copyright © Universal Images Group / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

9. Niels Bohr / Credit: WEBER COLLECTION / AMERICAN INSTITUTE OF PHYSICS / SCIENCE PHOTO LIBRARY / Universal Images Group / Copyright © Science Photo Library / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

10. Portrait of Sir James Chadwick, physicist / Credit: A. BARRINGTON BROWN / SCIENCE PHOTO LIBRARY / Universal Images Group / Copyright © Science Photo Library / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

11. Murray Gell-Mann, US physicist / Credit: EMILIO SEGRE VISUAL ARCHIVES/AMERICAN INSTITUTE OF PHYSICS/SCIENCE PHOTO LIBRARY / UIG / Copyright © Science Photo Library / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

12. George Zweig / Credit: Science Source / Photo Researchers / Universal Images Group / Copyright © Photo Researchers / For Education Use Only. This and millions of other educational images are available through Britannica Image Quest. For a free trial, please visit www.britannica.co.uk/trial

13. By alpinethread (Flickr) [CC BY-SA 2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons