Physics Universe - beta

The Atom

The word atom comes from the ancient greek meaning indivisible. The atom is the smallest particle that can be recongised as a chemical element. The element is made up of a nucleus of protons and neutrons with cloud electrons surrounding it. The protons within the nucleus are positively charged and the neutrons which are electrically neutral [or neutrally charged :) ]. The electrons around the outside of the nucleus are negatively charged. An atomic element is determined by the amount of protons and neutrons within it's nucleus. The amount of protons determine the chemical element and the number of neutrons determine the isotope.

The Nucleus

One of the most interesting discoveries about atoms is the fact that 99.9% of an atoms mass is located within the nucleus, with the mass divided up equally between the protons and the neutrons respectively. When the atom has a large nucleus the atom becomes unstable relative to its size. In such atoms the nucleus is subject to a process called radio active decay, where particles are emitted from the atoms.

The Electron Cloud

The electrons that surround the nucleus can orbit in a set of known levels. They can change from level to level depending on the amount of engery the electron has. Electrons gain and lose energy by absorbing and emitting energy. The electrons that orbit the nucleus determine the chemical properties of an element, and influence heavily the magnetic property of the atom.