Why is oxygen gas and titanium hard? Why does iron rust while gold does not? These and many other properties can be understood by knowing that the world is composed of atoms, which in turn combine to form molecules.
The idea of atoms as “indivisible particles” is ancient, and until the 19th century it never occurred to anyone that atoms themselves could be composed of particles. It wasn’t until after the discovery of electrons in 1897 that atoms were made up of negative and positive charges. Joseph Thomson, the discoverer of the electrons, postulated an evenly distributed positive charge where the negative electrons should be stuck like raisins in a cake. However, the New Zealand physicist was skeptical.
Born in New Zealand in 1871 and raised as one of twelve siblings, Ernest Rutherford was a pioneer from an early age. In 1908 he was awarded the Nobel Prize in Physics for his discovery of radioactive decay. However, it was not until after he received the award that his most famous experiment succeeded. On December 20, 1910, after several preliminary tests, he and two colleagues bombarded thin gold foil with high-energy alpha particles. Many particles flew unhindered through the gold foil, but some of them bounced off.
This was inconsistent with the corn raisin cake model. Rutherford reportedly commented on the result: “It is unlikely that you will hit a cotton ball with a revolver and the bullet will ricochet.”
The following year he published his new atomic model: all positive charge is concentrated in the nucleus of an atom in the centre, the nucleus, which contains almost all the mass. The electrodes orbit the core, but together they make up less than one-thousandth of the mass.
Compared to the dimensions of an atom, the nucleus is small, no larger than the head of a pin on a football field. Of course, this is not the end of the story. Later, electrons became probability clouds, and graphic images became mathematical equations. Thanks to Rutherford, even those with no mathematical knowledge were able to take a look inside the matter. Birgitte flock
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