Atoms are one of the smallest particles known. They are so small, that your average pinhead will have multiple millions of atoms. The atoms are listed in the periodic table, which lists 117 atoms and their atomic structures. In the table, they are referred to as elements like Oxygen, Helium (name of web-site) and Hydrogen. For this article, the atom of Helium will be looked at. An appropriate choice, considering this site's name.
All atoms, essentially, have the same basic structure. They are composed of protons, neutrons and electrons. There are a number of protons and neutrons within the center core, known as the nucleus. However, the atomic number can vary.
The atomic number is a reference to how many protons each atom has. It can be called the proton number. On the periodic table, they are used as a reference along with the letters. For example, Helium is represented as He and has an atomic number of two.
Another important number of the periodic table is that of mass number. This is the number of protons and neutrons combined. Protons are positively charged, while neutrons are neutral. The mass number of Helium is four, with two protons and two neutrons.
The third part of an atom is known as the electron, which is negatively charged. These electrons are not within the nucleus, but contained within an outer shell orbiting the nucleus. While the number of electrons atoms can have vary, they are all in layers of two in the first, eight in the second and eight in the third etc. Helium has two electrons, equal to its atomic number. The number of electrons is equal to the number of protons contained within an atom, which ensures that the atom is neutrally charged.
The basic structure of atoms, as referenced above, links atoms together to form molecules. A molecule, or particle, is a combination of atoms, like H2O. Water is composed of two Hydrogen atoms and one Oxygen atom, with Hydrogen and Oxygen bonded together via what is known as a chemical bond. Essentially this is when two or more atoms share electrons, which links them together.
Atomic structure has been manipulated in various forms, to give us two scientific advancements known as: nuclear fission and nuclear fusion. Nuclear fission essentially refers to the breaking up of the atomic structure (or atom) to release energy, via a chain reaction. Most famously used for one of the most destructive weapon devised by man: the nuclear bomb, first used in the Manhattan Project. Such a weapon releases a huge amount of radiation, along with invariable mass destruction to buildings and landscape. Nuclear energy is also used in power plants, and is cheap, although has proven occasionally unsafe as with the Chernobyl nuclear accident in Russia. Nuclear Fusion, is actually the opposite of Fission, and is used to fuse atoms together. This happens on the Sun, and releases energy. It has been used for the more destructive hydrogen bomb.
Admittedly, atomic structure and characteristics is not the most straightforward of subjects, but it has fascinated a generation of scientists. Although nuclear and atomic research has not always brought about the most beneficial advances, in the form of nuclear weapons, it has at least also provided largely stable nuclear generators, which are used throughout the world.