ATOMS PROJECT

CKS

ATOMISMATOMISM

Atomism is the theory that all the Atomism is the theory that all the objects in the universe are composed objects in the universe are composed of very small, indestructible building of very small, indestructible building blocks.blocks.

Atomism

Democritus and Leucippus taught that Democritus and Leucippus taught that the hidden substance in all physical the hidden substance in all physical objects consists of different objects consists of different arrangements of atoms. Democritus is arrangements of atoms. Democritus is given credit for the discovery of the given credit for the discovery of the model of atomism.model of atomism.

Earth, Wind, Fire, and WaterEarth, Wind, Fire, and Water

Aristotle came up with the idea that Aristotle came up with the idea that there were four different types of there were four different types of atoms. They were earth, wind, fire , and atoms. They were earth, wind, fire , and water.water.

Solid Sphere ModelSolid Sphere Model

In 1803, John Dalton viewed the atom as a small solid sphere. In 1803, John Dalton viewed the atom as a small solid sphere. Dalton believed that:Dalton believed that:

• Each element was composed of the same kind of atoms. Each element was composed of the same kind of atoms.

• Each element was composed of different kinds of atoms. Each element was composed of different kinds of atoms.

• Compounds are composed of atoms in specific ratios. Compounds are composed of atoms in specific ratios.

• Chemical reactions are rearrangements of atoms (mass is Chemical reactions are rearrangements of atoms (mass is conserved). conserved).

He came to this conclusion by careful analysisHe came to this conclusion by careful analysis

CathodeCathode Ray ExperimentRay Experiment

From observations made by J.J. Thomson From observations made by J.J. Thomson in the Cathode Ray Experiment he in the Cathode Ray Experiment he concluded that the particles inside were all concluded that the particles inside were all negatively charged. This led to the negatively charged. This led to the development of the Plum Pudding Modeldevelopment of the Plum Pudding Model

THE PLUM PUDDING MODEL

The The plum pudding modelplum pudding model of the of the atom was proposed by J. J. atom was proposed by J. J.

Thomson , who discovered the Thomson , who discovered the electron in 1897. Then later electron in 1897. Then later

Thomson proposed the plum Thomson proposed the plum pudding model in 1904. pudding model in 1904.

NUCLEAR MODELNUCLEAR MODEL

Ernest Rutherford created the Nuclear Ernest Rutherford created the Nuclear Model, by experimenting with the Gold Foil Model, by experimenting with the Gold Foil

Experiment, believing that most alpha Experiment, believing that most alpha particles passed through the foil but some of particles passed through the foil but some of

the particles bounced back the particles bounced back

Ernest Rutherford did a Ernest Rutherford did a brilliant experiment in which brilliant experiment in which he fired alpha particles at a he fired alpha particles at a very thin gold foil. He got a very thin gold foil. He got a somewhat shocking result: somewhat shocking result: rather than all the particle rather than all the particle passing straight through the passing straight through the foil, many were scattered off foil, many were scattered off at large angles, some even at large angles, some even coming straight back. This coming straight back. This led to the planetary model of led to the planetary model of the atom, with electrons the atom, with electrons orbiting the nucleus like orbiting the nucleus like planets orbiting the Sun. planets orbiting the Sun.

GOLD FOIL EXPERIMENT GOLD FOIL EXPERIMENT

Planetary ModelPlanetary Model

The most significant properties of The most significant properties of atomic and molecular structure may be atomic and molecular structure may be shown using a cut down picture of an shown using a cut down picture of an atom that is called the atom that is called the Bohr ModelBohr Model. This . This model was proposed by Niels Bohr in model was proposed by Niels Bohr in 1915. Which formally became known as 1915. Which formally became known as the the Planetary Model.Planetary Model.

The Electron Cloud ModelThe Electron Cloud Model

The electron cloud model evolved from The electron cloud model evolved from the earlier Bohr model. In the electron the earlier Bohr model. In the electron cloud model, rather than following fixed cloud model, rather than following fixed orbits, electrons bound to an atom are orbits, electrons bound to an atom are observed more frequently in certain observed more frequently in certain areas around the nucleus called areas around the nucleus called orbitals. The electron cloud can change orbitals. The electron cloud can change between electron orbital states, and between electron orbital states, and each state has a characteristic shape each state has a characteristic shape and energy.and energy.