The is the smallest unit into which any element can be broken down. The atom itself consists of a tiny , around which electrons orbit in [?]. The nucleus has a charge, while the electrons have a charge. In the atom, the positive and negative charges balance out.

In the nucleus, there are tiny particles called protons and neutrons. The has a positive charge, while the has zero charge. In the neutral atom, the number of protons is to the number of electrons.

A charged atom is called an . Positive ions occur when an electron is from the electron shells. ions happen when electrons are added to the electron shells. All atoms try to get their electron shell to the nearest gas structure. They do this by losing electrons, gaining electrons, or electrons. When electrons are gained or lost, the bonding is . If electrons are shared, the bonding is .

All chemical reactions involve movement of . Protons are never involved.