What are atoms
In 600 BCE, a famous philosopher from modern-day Gujarat, India, named Acharya Kanada Kashyapa proposed that small elementary particles exist in matter, which can be made into groups, which are molecules. He said that atoms are indivisible, which means that they cannot be cut any further into smaller particles. In 400 BCE, Democritus did the same as a greek philosopher.
More than 2,400 years later, John Dalton, a British chemist who was an English schoolteacher, said the same thing that Acharya Kanada Kashyap discovered, but named it Atomic Theory. Adding on the Acharya Kanada’s work, he said that the elements are just made up of 1 type of atom, and compounds are made up of 2 or more atoms, where the atoms can be same or different. He also said that all matter is made up of atoms, or the building block of matter.
All of these theories are mostly correct, but they all share the same mistake that an atom is indivisible. Many other scientists, like Ernest Rutherford, J.J. Thompson, and James Chadwick proved that atoms are divisible, and discovered particles called the subatomic particles. Today, scientists discovered even smaller particles called quarks and gluons, and many classes of particles like Leptons, Bosons, and Fermions.
The 3 main subatomic particles are Electrons, Protons, and Neutrons
The protons and neutrons make up the nucleus, which is the center of the atom. The nucleus is positively charged because protons are positive and neutrons and neutral charge. Electrons revolve around the nucleus in different shells.
Get Arav Govinda S’s stories in your inbox
Join Medium for free to get updates from this writer.
Inside protons and neutrons are particles called Quarks. Both protons and neutrons have 3 quarks each. A proton has 2 up quarks and 1 down quark, while a neutron has 2 down quarks and 1 up quark. Quarks can’t be divided into an even smaller particle that we know that have mass because Quarks are considered elementary particles. The electrons are just a type of lepton, which means that they have nothing to do with quarks and don’t interact through strong nuclear force. You can read more on this in my last blog article.
J.J. Thompson was once experimenting with phosphorescent screens, which were used as a technology for older Televisions and computers. He took one of those screens, which were also called Cathode Ray tubes, and observed the rays. He realized that there were negatively-charged particles being emitted through the rays, which were smaller than any atom. This was the very first proof that subatomic particles existed, and that there are things called electrons. He also tried to create a structure of the atom, where there is an ocean of electrons floating around within a sphere of positive charge, he called it the Plum Pudding model. Later on, Ernest Rutherford discovered the real atomic structure that we study today. Below is a picture of the plum pudding model.
The next great particle physicist was Ernest Rutherford. He proved that there was something called the nucleus by performing the Gold Foil experiment. In this experiment, there was a setup of the element radium, where alpha particles from the radium source were emitted towards a gold foil. Most of those particle passed straight through the middle of the gold foil, proving that the atom is mostly empty space, and created light, observed by the Zinc Sulfide ring around it. A few Alpha particles deflected in other directions, proving that there is a nucleus in the center.
James Chadwick, another great scientist, discovered neutrons. He did this by first producing some positively charged Alpha particles from the radioactive decay of Polonium. Then, he took some Beryllium atoms, and bombarded it with these alpha particles. This is resulted in a radiation with small neutral subatomic particles, which is known today as neutrons.
This is how the current atomic structure that we study came into being.
