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Atom Builder Challenge (Atomic Number, Mass Number, Proton, Electron, Neutron, Modern Periodic Table) | Chemistry | CK-12 Exploration Series

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Learn what makes each element unique by building the mystery atoms in the periodic table.

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The discovery process of the atom

1. Democritus (Ancient Greece) - Predict the presence of an atom

2. Dalton (UK, 1800) - Applied atomic chemistry

3. Krux (Britain, late 19th century) - Invented a cathode ray tube to explain various phenomena of electrons

4. Rutherford (Great Britain, 1909) - Confirming the existence of atomic nuclei

5. J. J. Thomson (UK, 1897) - Determination of the presence of electrons through a cathode ray tube experiment

6. N. Bohr (Denmark, 1913) - Planetary hypothesis of the atom

7. A. N. Bohr (Denmark, 1922) - Describing the shape of an atomic nucleus

8. de Broglie (France, 1923) - Propose the oscillation of electron particles

9. Schrödinger (Austria, 1926) - Mathematically identifying the electron orbits of an atom

10. Heisenberg (Germany, 1927) - Describes the stability of the electron orbit through the uncertainty principle

11. R. Feynman (USA, 1965) - Quantum Mechanics Research

12. IBM (USA, 1990) - Making a microscope capable of viewing atoms, succeeding in moving atoms into particles

Atomic model

What is the shape of the atom? The atomic model is a way of explaining what an atom looks like. The atomic model has been transformed as follows.

When We didn't know much about the atom, we thought it would be a solid lump like a billiard ball. However, real atoms can be divide into electrons and atomic nuclei, and using a particle accelerator can also divide atomic nuclei.

About 200 years ago, an atom was imagined to be like a muffin with raisins. The raisins on the outside of a muffin can be compared to the electron. Positive charges within an atom are spread throughout the entire volume, and electrons were thought to oscillate around fixed points within a cation (muffin).

One hundred years ago, it was discovered by Rutherford that most of the atoms were empty.

After that, Niels Bohr presented a more refined atomic model. Bohr's atomic model is very close to the atomic model that can be seen these days. In Bohr's atomic model, electrons are in a given orbit. This model is also called a planetary model because electrons orbiting around an atomic nucleus resemble a planet orbiting the sun.

Currently, it is known that electrons around an atomic nucleus have the properties of matter and wave at the same time, and the position and speed of electrons cannot be accurately known at the same time and can only be grasped with statistical probability.

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The discovery process of the atom Democritus (Ancient Greece) - Predict the presence of an atom Dalton (UK, 1800) - Applied atomic chemistry Krux (Britain, late 19th century) - Invented a cathode ray tube to explain various phenomena of electrons...

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Discovery of nuclei

At the beginning of the 20th century, little was known about atoms' structure, except that atoms contain electrons.
At the time, the atom was thought to be as a model of pudding containing raisins. According to this model, positive charges in an atom are evenly spread throughout the entire volume, and electrons (raisins) are thought to oscillate around fixed points in a sphere of charge (pudding).

In 1911, Rutherford experimented with colliding powerful α-particles (the nuclei of helium) into thin pieces of gold foil.
Α-particles that are 7300 times heavier than electrons have a charge of +2e and are naturally released with the energy of several MeVs from many radioactive materials.
With this experiment, Rutherford attempted to measure how much α-particles bend as they pass through a piece of gold leaf.

As a result of the experiment, most α-particles are scattered at small angles, but surprisingly, tiny amounts of α-particles are scattered at large angles close to 180 degrees.
Through this experiment, humankind became aware of the existence of an atomic nucleus.
Analyzing the results of the experiment, Rutherford came to the following conclusion:

"The radius of the nucleus must be much smaller than that of the atom, and the ratio is about 10 ⁴. In other words, most of the atoms are made up of empty spaces."

It is not uncommon to draw such important conclusions from a brilliant scientist's keen insights and a few simple calculations.

An experimental device used to test the scattering of α (alpha) particles by a thin piece of gold foil. The detector can be rotated with several scattering angles. The atomic nucleus was discovered with such a simple experimental device.

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Discovery of nuclei At the beginning of the 20th century, little was known about atoms' structure, except that atoms contain electrons. At the time, the atom was thought to be as a model of pudding containing raisins. According to this...

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A clear animation and some slides describing the fission process.

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When two light nuclei join to form a heavier 	nucleus

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When two light nuclei join to form a heavier 	nucleus