Atomic Theory in a Nutshell

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440BC 350BC 1803 1900 1909 Democritus – Aristotle –

everything made up of 4 elements – earth, air, fire, water

Alchemists –

Discovered medicines, acids and tried to turn materials into gold. Discovered

“pure” substances

and said there are a lot more than just 4 elements. Were first to id the chem. and phy properties of elements

John Dalton –

up with the

Atomic Theory in a Nutshell

“atomos” – everything made up of tiny building blocks mixed different materials together to make new materials. “Father of Modern Chemistry” – atoms are like different elements are different

J. J. Thomson – “Plum Pudding Model” –

negative and a positive found the atom had

solid billiard balls –

atoms of the same element are the same; atoms of Worked with the CRT (cathode ray tube) and came

2 parts

– a

Ernie Rutherford –

Made a radio active gun and shot radiation at a sheet of gold foil. Came up with the

Solar System Model

– the atom is mostly empty space with a positive center and negative particles orbiting around it like planets around the sun.

1913 1920-30 Neils Bohr – Electron Cloud Model

moving so quickly that we can’t predict where they are – we can only guess where they are likely to be. This is the model we use today. said the particles are so tiny and

Electron Cloud Model

sees a atom with a solid center and a fuzzy area with negative particles around it.

Schroedinger/Heisenberg -

Electron Cloud Model…Said the particles are so tiney and moving so quickly that we can’t predict where they are- we can only guess where they are likely to be. Electron Cloud Model sees and atom with a solid center and a fuzzy area with negative particles around it. This is the model we use today.

1932 James Chadwick –

Discovered the

neutron.

By 1932 we knew the Atom had 2 parts (

protons, located in the nucleus

or center of the atom and

electrons, located outside the nucleus

). The electrons were kept in place by the protons as

opposite charges attract

. But what kept the protons together inside the nucleus? They should have

repelled

each other. By studying the weight of atoms, he found that protons were held in place by another particle he called “neutron” as they were “neutral” – they had no charge. For every proton there was a neutron that separated it from another neutron keeping the neutrons in place inside the nucleus

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