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it is on structure of an atom


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Atomic Models:

Atomic Models This model of the atom may look familiar to you. This is the Bohr model. In this model, the nucleus is orbited by electrons, which are in different energy levels.

Who are these men?:

Who are these men? In this lesson, we’ll learn about the men whose quests for knowledge about the fundamental nature of the universe helped define our views. DALTON J.J.THOMSON RUTHERFORD NEIL BOHR

Dalton’s atomic theory:

Dalton’s atomic theory All matter is made of very tiny particles called atoms. Atoms are indivisible particles, which cannot be created or destroyed in any chemical reaction. Atoms of given element are identical in mass and chemical properties. Atoms of different elements have different masses and chemical properties. Atoms combine in the ratio of small whole numbers to form compounds. The relative number and kinds of atoms are constant in a given compound.

J.J.Thomson’s Model:

J.J.Thomson’s Model In 1897 , the English scientist J.J. Thomson provided the first hint that an atom is made of even smaller particles.


OBSERVATION An atom consists of a positively charged sphere and the electrons are embedded in it. The negative and positive charges are equal in magnitude. So, the atom as a whole is electrically neutral.

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Thomson concluded that the negative charges came from within the atom. A particle smaller than an atom had to exist . The atom was divisible! Thomson called the negatively charged “ corpuscles, ” today known as electrons . Since the gas was known to be neutral, having no charge, he reasoned that there must be positively charged particles in the atom. But he could never find them.

Rutherford’s Gold Foil Experiment:

Rutherford’s Gold Foil Experiment In 1908, the English physicist Ernest Rutherford was hard at work on an experiment that seemed to have little to do with unraveling the mysteries of the atomic structure.

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Rutherford’s experiment Involved firing a stream of tiny positively charged particles at a thin sheet of gold foil (2000 atoms thick) Most of the positively charged “bullets” passed right through the gold atoms in the sheet of gold foil without changing course at all. Some of the positively charged “bullets,” however, did bounce away from the gold sheet as if they had hit something solid . He knew that positive charges repel positive charges.

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This could only mean that the gold atoms in the sheet were mostly open space . Atoms were not a pudding filled with a positively charged material. Rutherford concluded that an atom had a small, dense, positively charged center that repelled his positively charged “bullets.” He called the center of the atom the “ nucleus ” The nucleus is tiny compared to the atom as a whole.


Rutherford Rutherford reasoned that all of an atom’s positively charged particles were contained in the nucleus. The negatively charged particles were scattered outside the nucleus around the atom’s edge .

Bohr Model:

Bohr Model In 1913, the Danish scientist Niels Bohr proposed an improvement. In his model, he placed each electron in a specific energy level.

Bohr Model:

Bohr Model According to Bohr’s atomic model, electrons move in definite orbits around the nucleus, much like planets circle the sun. These orbits, or energy levels , are located at certain distances from the nucleus.


ACKNOWLEDGEMENT THANK YOU… I want to say thank’s to my teacher Mrs. Charu Bhatnagar To give me this powerpoint presentation project

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