Once nobody know about the atom. Nobody knew it was there, and nobody really thought about it. Then, some scientists got curious and started researching. One of these scientist was Ernest Rutherford.
Rutherford’s experiments led to the discovery of the nucleus. Since a few positively charged particles bounced back from the foil, Rutherford concluded that such particles were repelled by densely packed regions of positive charge. Most particles fired at metal foil passed straight through, so Rutherford concluded that atoms were mostly empty space. Experiments with the cathode ray led to the discovery of the small particles called electrons.
The atom was also found to have multiple particles inside it. These particles include protons, neutrons, and electrons. Protons are positively charged and found in the nucleus. However, the neutrons don’t have a charge and are also found in the nucleus. Most people would assume that this would make the atom positively charged. This is not true though. The electrons orbiting around the nucleus are negatively charged and balance out the charge.
The protons and electrons in an atom are always equal. Also, in every isotope, the atomic number will always be the same for each atom molecule that is the same type of elements. However, the atomic mass of each of these atoms can differ. Atomic mass is the amount of protons and neutrons added together. The amount of neutrons in atoms can change will have no effect on the atom besides the fact that the atomic mass increases. The protons and neutrons stay the same when the mass number rises.
According to Dalton’s atomic theory, atoms of each element are equal in size, mass, and other properties. This theory helped explain the Law Of Conservation Of Mass. It stated that atoms could not be created or destroyed. The Law Of Conservation Of Mass follows the belief that atoms are indivisible. However, Dalton’s theory never followed the idea that atoms are combined, separated, and rearranged during chemical reactions. If you compare Dalton’s theory to the current modern day atomic theory, everything was basically the same except Dalton believed that all atoms of the same element have the same mass and they do not.
Thompson’s atomic theory was created in 1903. His model was known as the plum pudding model. Thompson changed the appearance of the atom because he discovered the electron. The atom was no longer thought to look like a small solid ball anymore. His theory suggested that there were protons and electrons within the atom. It also suggested that the atom was indivisible.
From starting at not knowing what an atom was and not knowing it existed, we have came a long way. It’s amazing what you can find out by doing experimentations in science. 🙂