History of the Atom

Flashcards covering key concepts in the history of atomic theory from Dalton to modern advancements.

John Dalton

Proposed in 1803 that elements are made of spherical atoms.

J.J. Thompson

Discovered the electron in 1897 and created the Plum Pudding Model.

Plum Pudding Model

A model of the atom where negative electrons are embedded within a positively charged 'pudding'.

Ernest Rutherford

Discovered the nucleus in 1909 and concluded that atoms are mostly empty space.

Gold Leaf Experiment

Experiment by Rutherford where alpha particles (positively charged particles) were fired at a thin slice of gold leaf (positively charged nucleus) to demonstrate the presence of the nucleus.

The large deflections of the alpha particles were explained by the strong electrostatic repulsion between the positively charged alpha particles and the positively charged nucleus of the gold atoms.

https://flexbooks.ck12.org/cbook/ck-12-chemistry-flexbook-2.0/section/4.14/primary/lesson/rutherfords-atomic-model-chem/

Niels Bohr

Proposed in 1913 that electrons exist in shells around the nucleus, discovered with his EM radiation experiments.

What is the Electromagnetic Radiation (EM) experiment?

EM radiation was absorbed by electrons, which caused them to move between shells, and emit the radiation as they moved to lower energy levels. This proved electrons existed within shells and were not free-floating.

Electron Shells

Regions where electrons reside around the nucleus, proposed by Bohr after his EM radiation experiments.

Subshells

Subdivisions within electron shells that have different energy levels, recognized after Bohr's model; a modern discovery.

Current Atomic Model

Refers to the updated understanding of atomic structure including subshells and varying energy within the shells.