Question

A good theory in science simultaneously is consistent with previous observations and makes predictions that can be tested through future observation and, ideally, experiments. That is, a scientific theory needs to be testable. Atomic theory - that is, an atom is the smallest division of an element that retains the chemical properties of the element and is too small to be seen - cannot be tested using by sight, not even using an optical microscope. Pay attention to the various forms of evidence that atoms exist. What kinds of technology are needed to show atoms exist? What kinds of indirect observations were made? In your first post of this discussion, please communicate one piece of evidence for the existence of atoms: describe briefly what the evidence is and where you read about it.

Answer 1

The curiosity to know about the building block of matter fascinated many scientists. They began to find out the structure of an atom. Gilbert Lewis gave the cubical model of an atom. J.J. Thomson, who discovered an electron gave the plum pudding model. Saturnian Model was given by Hantaro Nagaoka. It was in 1913 that Neils Bohr and Rutherford gave the Bohr Model, in which Rydberg formula was explained for the spectral lines of the hydrogen atom.

Human eye is far more limited than scientific instruments. This is exactly the reason why we can't see an atom with our naked eye but only using modern equipments. Quantum theory, a branch of theoretical physics, was developed to understand the fundamental properties of matter.

With the help of quantum mechanical model of atoms, we get the details of atomic spectra. SEM i.e. Scanning Electron Microscope uses a highly coherent beam of electrons to scan even the elevation map of the surfaces. The nanotip of SEM can detect the presence of individual atoms on the surface of the sample to be tested. The monolayer crystal growth technology enables the deposition of single layer of atoms on the required surface. AFM i.e. Atomic Force Microscopy, a type of scanning probe microscope has the power to demonstrate at the level of fraction of a nanometer. The AFM tip has thickness range in the order of few atoms. This is possible only with the advancement of technology. Over the period of time, many scientists have contributed a lot in this field of nanotechnology. Scientists in 1989 managed to write the name of their company "IBM" using 35 individual atoms on a nickel substrate with the help of STM i.e. Scanning Tunneling Micrscope. This was one piece of evidence for the existence of atoms. I read about this scientific evidence in one of my courses.

Every material has a unique raman spectra. Materials having same set of atoms but different orientation can now be distinguised using Raman spectroscopy by taking into account the characteristic peak of their respective raman spectra.

As Feynman said "There's plenty of room at the bottom" in one of his lectures, there is indeed a huge scope at the atomic level and much more research needs to be done, in order to get the true picture of the atoms in the sub atomic level.