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Make this table in your iSN. How did we figure out these very, very, small particles existed? As we go, 1) check the boxes that apply in your table 2) draw a diagram for each model. Atom Videos: Nanotechnology. How small are atoms? atom.

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Make this table in your iSN

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Make this table in your iSN

How did we figure out these very, very, small particles existed? As we go, 1) check the boxes that apply in your table2) draw a diagram for each model.

Atom Videos: Nanotechnology

How small are atoms?


Atoms are so small it is difficult to imagine.

Atoms are mostly empty space. Drawings of the atom don’t show his because otherwise the nucleus would not be visible.

The nucleus is very dense!

Which is smaller, a cell or an atom? Also…they both have a nucleus?

Nucleus = the centerNucleus of a cell contains DNA which contains atoms.Everything else in the cell is made of atoms.

The nucleus of an atom contains protons and neutronsAn atom is 1,000,000 times smaller than a cell!

Greek Model

  • Democritis- Greek philosopher

  • 400 BC

  • Idea of ‘atomos’ – at some point, matter cannot be further divided

  • Based on philosophy, not science

This theory was ignored and forgotten for more than 2000 years!

Dalton’s Theory- 1803

  • All elements are made of atoms. Atoms can’t be divided or destroyed.

  • Atoms of the same element are exactly alike.

  • Atoms of different elements are different.

  • Compounds are formed by the joining of atoms of two or more elements.

Thomson Model- 1897

  • PlumPuddingmodel.

  • Atoms were made from a positively chargedsubstance with negatively charged electrons scattered about, like raisins in a pudding.


  • ****positively charged particles were contained in the nucleus.

  • negatively charged particles were scattered outside the nucleus around the atom’s edge.

Gold Foil Experiment

Bohr Model- 1913

  • The electrons move in energy levels

  • located at specificdistances from the nucleus.

1925- Electron Cloud Model

  • it is impossible to determine the exact location of an electron, but we can estimate probabilities.

  • More complex than energy levels.

  • According to the modern atomic model, at atom has a small positively charged nucleus surrounded by a large cloud-like region of electrons

What does your table look like?

We have seen several atomic ‘models.’What is the scientific definition of a model?When would you use a model?Can we think of other examples of models?

The Electron Cloud model is the newest model. 1) Does that make it the ‘best.’2) Why is it useful to look at the other models?

Want to learn more?

Search terms for your investigation:

Democritus – Billiard ball model

John Dalton

JJ. Thomson – plum pudding model

Ernest Rutherford- Gold Foil Experiment

Inside of protons and neutrons- Quarks, Gluons

Details on experiments- Glencoe book pg62-74

How is an atom held together?

Then…how is the Nucleus Held Together?

Then…how is the Nucleus Held Together?

In sum, the force holding the nucleus together is stronger than the repulsive force of the positively charged protons.

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