H O W T H E A T O M W A S O N C E I D E A L I Z E D T OB E K N O W N A S W E K N O W I T T O D A Y ?

Atomic theory

Chemistry 1

Etymology

Indian Greek

By the end of 2nd centuryB.C. Kanada believedthat matter was composedby “Atoms” grouped intomore complexed objects.

By the 5th century B.C. Democritus stated that smallparticles called “Atoms” werepresent in all types of matterand their constantly changingtheir arrange.

Philosophical atomism

Ishvara Democritus

E X P E R I M E N T A L E V I D E N C E S H O W S N E W I D E A S A B O U T A T O M S A N D C O M P O U N D S

Modern Atomic Theory

Modern Atomic theory

1789 and 1799 laws by Lavoisier and Proust

1808 Atomic model by John Dalton

1897 J.J Thomson the “Plumb Pudding”

1909 Ernest Rutherford discovered the nucleus

1913 Niels Bohr “The Bohr model”

1918 Rutherford “strikes again” with the protons

1932 James Chadwick and the neutrons

1924 Louis de Broglie and the orbitals

Two fundamental laws appear

1789 Antoine Lavoisier stablished the “Law of conservation of mass”

1799 Joseph Proust stablished the “law of definiteproportions”

Joseph Proust

Antoine Lavoisier

Two fundamental laws appear

“Law of conservation of mass”

“Law of definite proportions”

1808 Dalton´s Theory

“chemical element is composed of atoms of a single, unique type, and they cannot be altered or destroyed by chemical means, they can combine to form more complex structures”

John Dalton

Dalton Theory

The Subatomic particles age

By 1887 J.J. Thomson breaks down the idea thatthe atom was undivisible and discovers theELECTRONS

J.J. Thomson

The Plumb Pudding

Positive charged cloud

Negative charged corpuscles

Ernest Rutherford Model

By 1909 Rutherford working with alfa particlesdiscovered the positive charged nucleus of the atomand stablished the “Planetary model”

Ernest Rutherford

The Rutherford experiment

Thompson Model

Rutherford Model

Alfa particlesheavily

deflected

The “Planetary Model”

Nucleus

Electron cloud

The Bohr reafirmation

At 1916 Niels Bohr based on the “Quantum theory” justify the steady orbit of the electrons and stablishthat orbitals of diferent levels of energy surround thenucleus and electrons move around them

Niels Bohr

Niels Bohr and Albert Einsten

The Bohr Atomic model

Bohr atomic model

Building the nucleus, Rutherford strikes again!

In 1918, Rutherford bombarded nitrogen with alfa particles, analyzing and realizing that he succesfullydivided the nucleus into smaller positive chargedparticles called: “Protons”

Ernest Rutherford at 1918

Case pending

Protons didn´t complete the weight of the nucleus by themselves

Rutherford suggest that this mass couldbeen completed in the nucleus by

particles without charge

Discovery of neutrons

Walther Bothe by 1928 discovers that Beriliumemitted neutral charged beams when bombed withalfa particles.

James Chadwick finds neutral beams to be particleswith a similar mass of a proton.

Walther BotheJames Chadwick

The Atom

So, this is the Atom, as we know now.

Electron

Nucleus with sameproportion of Neutrons

and protons

Electronic orbitals