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Presentation

ATOMIC MODELS

Hector Fdez, Rayan el Mouden

Start

INDEX

Bohr model

Dalton atomic theory

Timeline

Thomson Model

Ending

Thomson Experiment

Rutherford Model

Gold foil experiment

dalton atomic theory

1. All matter is composed of tiny indivisible particles called atoms. 2. Atoms of a given element are identical in size, mass, and other properties 3. Atoms of different elements differ in their properties 4. Atoms cannot be created, divided, or destroyed in chemical reactions 5. Atoms combine in simple whole-number ratios to form compounds.

SIGNIFICANCE OF DALTON ATOMIC THEORY

1. Foundation of Chemistry: It was the first scientific theory to explain the nature of matter at the atomic level. 2. Law of Conservation of Mass: Provided a microscopic explanation for this law. 3. Law of Definite Proportions: Explained why compounds are formed in consistent proportions by weight.

THOMSON MODEL

1. Atoms are made of a uniformly distributed positive charge.2. Electrons are embedded within this positive charge 3. The atom is electrically neutral.

THOMSON EXPERIMENT

1. Generation of Cathode Rays 2. Observation of Deflection 3. Measurement of Charge-to-Mass Ratio 4. Independence of the Cathode Material He discovered that cathode rays were made up of negatively charged particles. Called electrons

BOHR MODEL

-Rutherford’s model could not explain atomic collapse and atomic spectra:

• ATOMIC COLLAPSE: every charged particle under acceleration emits energy.It should emit energy, lose speed and end up falling into the nucleus,but this doesn´t happen
• ATOMIC SPECTRA: when the electron leaps between orbits, it absorbs or releases energy.So we have a release of electromagnetic,with the atomic spectrum discontinous

-In 1913, Niels Bohr used quantisation which consists in assuming that magnitudes don´t evolve continously,he postulates

• Electrons describe circular orbits around the
• nucleus without radiating energy.
• Only a few orbits are allowed.
• The electron only emits or absorbs energy in the jumps from one allowed orbit to another, the energy emitted/absorbed being the difference in energy between the two levels.

RUTHERFORD MODEL

-IN 1911, AFTER THE GOLD FOIL EXPERIMENT,RUTHERFORD POSTULATES:

• THE ATOM CONSISTS OF A NUCLEUS

• VERY SMALL COMPARED TO THE SIZE OF THE ATOM

• POSITIVELY CHARGED AND WHERE ALMOST OF ITS MASS IS CONCENTRATES

• NEGATIVELY CHARGED ELECTRONS REVOLVE AROUND THE NUCLEUS

-IT WAS PARTIALY MODIFIED YEARS LATER WITH THE DISCOVERY OF THE NEUTRON,IN 1932

Gold foil experiment

-IN 1911,RUTHERFORD AND HIS STUDENTS CONDUCTED THIS EXPERIMENT THAT CONSISTS ON:

• Bombarding a thin gold foil
• With very small, positively charged alpha particles

-INTERPRETATION OF THE RESULTS :

• no deflections or bouncing of the incident particle is being observed.
• The particles are deflected by encountering a very small positively charged area
• where most of the mass of the atom is concentrated.

timeline

Dalton

1803

RUTHERFORD

1911

And leave youraudience amazed

Thomson model

1904

Bohr

1913

THANKS FORLISTENING