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Atoms and their structure
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Some drops would hover

Slide 25

Millikans Experiment

Millikans Experiment

From the mass of the drop and the charge on

the plates, he calculated the charge on an electron

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Slide 26

Rutherfords Experiment

Rutherfords Experiment

Ernest Rutherford English physicist. (1910)

Believed the plum pudding model of the atom was correct.

Wanted to see how big they are.

Used radioactivity.

Alpha particles - positively charged pieces given off by uranium.

Shot them at gold foil which can be made a few atoms thick.

Slide 27

Rutherfords experiment

Rutherfords experiment

When the alpha particles hit a florescent screen, it glows.

Heres what it looked like (pg 72)

Slide 28

Lead block

Lead block

Uranium

Gold Foil

Flourescent

Screen

Slide 29

He Expected

He Expected

The alpha particles to pass through without changing direction very much.

Because

The positive charges were spread out evenly. Alone they were not enough to stop the alpha particles.

Slide 30

What he expected

What he expected

Slide 31

Because

Because

Slide 32

Because, he thought the mass was evenly distributed in the atom

Because, he thought the mass was evenly distributed in the atom

Slide 33

Because, he thought the mass was evenly distributed in the atom

Because, he thought the mass was evenly distributed in the atom

Slide 34

What he got

What he got

Slide 35

How he explained it

How he explained it

Atom is mostly empty.

Small dense, positive piece at center.

Alpha particles are deflected by it if they get close enough.

Slide 36

He Expected

Slide 37

Modern View

Modern View

The atom is mostly empty space.

Two regions.

Nucleus- protons and neutrons.

Electron cloud- region where you might find an electron.

Slide 38

Density and the Atom

Density and the Atom

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