Ionic Bonds

Molecular Cations and Anions

Molecules can also lose or gain electrons to become cations or anions. For example, the NO₃ molecule will gain an electron to form the nitrate anion.

If you count up all of the electrons you'll find that all of the atoms feel like neon.

Here is the ammonium ion, an example of a molecular cation.

The ammonium ion has given up an electron to become a cation.

Ionic Bonds

Ionic bonds are generally formed when you bring atoms which really want to lose electrons together with atoms which really want to gain electrons.

The Na⁺ cation and the Cl^- anion are held together by electrostatic or ionic bonds. There is no sharing in ionic bonding. The anion takes the electron for itself and the cation is happy to get rid of its electron. The ions in ionic compounds are arranged in three-dimensional structures. There are no discrete molecules of NaCl. We can only write an empirical formula of NaCl.

Here are some other examples.

All substances are electrically neutral. We can use this fact to obtain the chemical formula of an ionic compound.

Notice that in Na₂S, two sodium cations were needed to balance the -2 charge of S^2-, making things electrically neutral.