Ions and compounds
Atoms are made up of neutrons that are neutral and have no charge, protons with a positive charge andelectrons with a negative charge.
An ion is an entity or a group of atoms with a positive or negative charge such as the positively charged hydrogen ion H+ and thenegatively charged nitrate ion NO3-. Negatively charged ions are also called anions while positively charged ions are called cations.
A compound is something that is made up oftwo or more simple substances. Ammonia NH3 is a compound without a charge.
Below it is shown how positively charged protons (yellow) and neutral neutrons constitutes a nucleusin the atom while the negatively charges electrons orbits the nucleus. This is a very simple model of the atom.A more complicated model would include a nucleus surrounded by orbitals with electrons in them orbiting the nucleus.
A philosophical approach to atoms
A full course about atoms and ions
Encarta - encyclopedia