How Do Cations Form?

When Elements Combine

• Non-metallic atoms have the ability to attract electrons. When this occurs, the ion is called an anion because it gains an electron. Subsequently, when metallic and nonmetallic elements unite, the non-metallic element is strong enough to pull electrons from the metallic element to form an ion. The newly formed cation and anions are attracted to each other to form ionic bonds.

Ionic Bonding

• An ionic bond is formed when electrons in the outer shell are entirely transferred from one atom to the other. The reacting atoms form the ions. The positive and negatively charged ions are brought together through electrostatic forces. For example, sodium chloride (NaCl) is formed by an ionic bond. Sodium has one electron in its outer shell, while chlorine has seven electrons in its outer shell. To create sodium chloride, the sodium must give up its electron to the chlorine atom. The sodium becomes positively charged because it lost an electron, while the chlorine is now negatively charged because it gained an electron. The two can combine to form sodium chloride -- a more stable compound.

Determining the Charge

• You can calculate the charge an ion has based on where the element is located on the periodic table. Alkali metals in Group 1A, like hydrogen and sodium, lose one electron to form a cation that possesses a 1+ charge. The Group 2A elements (the alkaline earth metals like magnesium and calcium) lose two electrons to form a cation with a 2+ charge. An element in the Group 3A family, like aluminum, will lose 3 electrons to form a 3+ cation.

Features of Ionic Compounds

• Compounds held together by ionic bonding have several things in common. The bonds are always formed between a metal and a nonmetal. Additionally, the metal is always listed first, like in sodium chloride. Ionic compounds also are good conductors of electricity, can dissolve readily in water and are able to form crystalline solids capable of high meting temperatures.