Ions and compounds

Atoms are made up of neutrons that are neutral and have no charge, protons with a positive charge and electrons 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 the negatively 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 of two or more simple substances. Ammonia NH₃ is a compound without a charge.

Atom model

Below it is shown how positively charged protons (yellow) and neutral neutrons constitutes a nucleus in 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.

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Web resources

A philosophical approach to atoms
A full course about atoms and ions
Encarta - encyclopedia