WHAT IS AN ATOM?Atoms are the smallest indivisible particle of matter in the world. More simply, atoms are the basic building blocks of ordinary matter. Matter, is anything that has mass and takes up space. Atoms can join together to form molecules, which in turn form most of the objects around you. WHAT IS THE ATOMIC MODEL?The atomic model is a model/image, of what the atom looks like. For example, one model said that the atom had a positive charge and that electrons are negatively charged. The atomic model can be shown in many ways, diagrams, pictures, sculptures.
It just has to be a way of showing what the atom looks like, and what it contains inside of it.THE HISTORY OF THE ATOMIC MODELIn the year 460 BC, a Greek man named democritus, proposed that all matter, including space and time, was made of up small units called atoms. He had no evidence and had done no experiments, but his idea was taken into consideration by the people at the time, as no such idea was ever thought of.
The theory of the atom, remained untouched for many years, until in 1806, an English chemist, John Dalton, stated that all matter was created by atoms, which he believed, were indestructible. He also stated that compounds are created by combining two atoms. He was the first person in the modern world, to really start to think about the atom. He made people begin to think about the atom, and start to experiment with it. In 1869, the experiments and research into the atom, really started to kick off. A Russian chemist, Dmitri Mendeleev created the periodic table of elements.
He based this table of elements, on atoms. He added an atomic number, to each element. This number contained information on the number of protons and neutrons and electrons in an element, although this information changed over time, as the model of the atom, and its ideological structure changed too. In the year 1885, Eugene Goldstein, discovered that there were positive particles. He also said that the particles had a charge equal and opposite to the electron.
The first idea of what the atom looks like, was conceived by JJ Thomson in 1904. He discovered the electron, by experimenting with a vacuum cathode ray tube. He thought that atoms were only composed of electrons and negative charges. He was the first person to make a definitive picture of the atom. He saw it as a positively charged big atom, containing many small parts with negative charges inside of it.
This theory was then proven wrong by Ernest Rutherford in 1911 in an experiment called the gold foil experiment. In this experiment, Rutherford shot alpha particles (A positive particle consisting of two protons and two neutrons), at a sheet of gold foil. He noticed that some particles went through and some bounced back, implying the existence of a positive nucleus.Two years later, In 1913, Niels Bohr proposed a model of the atom where there was a proton at the nucleus and the electrons orbited around the nucleus.
He said it was impossible for the negative electrons proposed by Rutherford, to exist, as the negative electrons would be drawn to the positive nucleus, and the atom would collapse in on itself.In 1932, a British Physicist named James Chadwick, Discovered the Neutron. He said that the neutron helps balance out protons in the nucleus of an atom.HOW HAS TECHNOLOGY HELPED TO DEVELOP OUR PICTURE OF THE ATOM?The Electron Microscope can not only let us see objects to incredible magnification, but it can also help us see individual atoms. Specifically the “Nion Hermes Scanning Transmission Electron Microscope”, one of only 3 in the world. This microscope, can view almost any material down to the atomic scale.
This is all possible because electron microscopes use a beam of electrons rather than photons, as you’d find in a regular light microscope. As electrons have a much shorter wavelength than photons, you can get much greater magnification and better resolution. Why would anyone even want to see something to such a high degree of magnification? Well this is because the technology industry, is trying to miniaturize devices. They need to miniaturize parts like transistors and semiconductors. Modifying a material even by an atom or two could change its properties. When you can see the atoms, it becomes a lot easier to move them around. For example, let’s take graphene.
A 2D sheet of carbon atoms. Add another atom here or there and you’ve changed the material and potentially modified what it can do. For this reason, it is crucial to keep an eye on the structure, because a single atom could ruin material or it’s intended use.