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.

alternatetext

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.

alternatetext

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

  • Molecular Cations and Anions:

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.

alternatetext

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.

NH4Cl : here NH4+= cation
here Cl-= anion
BaCl2 : here Ba2+= cation
here Cl-= anion

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

Ba2+andSO42-formBaSO4
Na+andS2-formNa2S

Notice that in Na2S, two sodium cations were needed to balance the -2 charge of S2-, making things electrically neutral.

Homework from Chemisty, The Central Science, 10th Ed.

2.39, 2.41, 2.43, 2.45, 2.53, 2.55