All substances consist of molecules. Various studies have shown that molecules of the same substance are absolutely identical: any pure substance is composed of molecules, which are peculiar only to him. However, the substance is different from the others, as they consist of different atoms, which when connected form a variety of molecules. Though the molecules themselves are very small, but they can share. Share they particles, which when connected form a variety of molecules.
Even the ancient Greeks knew that all matter consists of tiny particles invisible to the human eye, which are called atoms. However, they mistakenly believed that the atom is the smallest indivisible particle ("atom" in translation from Greek means "indivisible"). Modern scientists know that the atom consists of a small, but very heavy nuclei, located in the center, and electronsmoving around the nucleus. It is the electrons fasten the individual atoms in the molecule, forming a new substance. Various substances are composed of different atoms, different core size and number of electrons. Thus the smaller the atom the electrons, the easier stuff. For example, in the hydrogen atom only has one electron.