Complete the exercises below. a. Using Werner’s definition of valence, which property is the same as oxidation number, primary valence or secondary valence? b. What term do we normally use for the other type of valence? c. Why can NH₃ serve as a ligand but BH₃ cannot?

Werner's theory distinguishes between primary and secondary valences in coordination compounds. Primary valence corresponds to the oxidation state of the central metal ion, while secondary valence refers to the number of ligands attached to the metal. This framework helps in understanding the bonding and structure of complex ions.

Ligands are molecules or ions that can donate a pair of electrons to a central metal atom to form a coordination complex. The ability of a substance to act as a ligand depends on its electron-donating capacity and steric factors. For example, NH₃ can donate a lone pair of electrons, while BH₃, being electron-deficient, cannot act as a ligand.

The oxidation number is a concept used to indicate the degree of oxidation of an atom in a compound. It reflects the number of electrons an atom can gain, lose, or share when forming chemical bonds. In coordination chemistry, the oxidation number of the central metal ion is crucial for determining its reactivity and the overall charge of the complex.