Earth Site Education

It was believed for a thousand years that atoms were the smallest component of matter, but in the late 19th century, the first evidence that atoms were made up of smaller sub-atomic particles came to light.     About Atoms Diagram of an atom Electrons Discovery of Electrons Properties of Electrons Protons Discovery of Protons Properties of Protons Neutrons Discovery of Neutrons Properties of Protons     About Atoms         It has been known for a thousand years that all matter is made up of small particles known as atoms, but for much of this time, it was believed that atoms were the smallest component of matter. It was not until the late 19th and early 20th century that the first evidence that atoms were made up of smaller sub-atomic particles came to light.         A = The Nucleus of the atom contains the protons and neutrons. Despite accounting for the majority of an atom’s mass, the nucleus occupies a minute proportion of the total space. The Diameter of the nucleus is approximately 4 femtometres or 4 x 10-15 meters. It is very difficult to measure the diameter of the nucleus because, like our atmosphere, it has no defined edge but gradually fades away.   B = This is mainly just empty space where the electrons orbit the nucleus. Its diameter (and that of the whole atom) is 0.1 nanometres or 0.1 x 10-9 meters.         Here is the chemical symbol for helium as you might see it on a periodic table. The number at the top is known as...