Chapter U1.23, Problem 2E

Interpretation Introduction

Interpretation:

Method to determine the charge on a transition metal cation from chemical formula is to be explained.

Concept introduction:

Metals which are located in the middle of the periodic table are called transition metals. These metals are brightly colored so they are used in paints and pigments. Many such metals we use in our daily life are copper, iron, nickel, silver and gold.

Answer to Problem 2E

To determine the charge on transition metal cations, one uses the charges on known ions and apply the rule of zero charge. one can find out of the charge on known ion from the periodic table. According to rule of zero charge, the total charges on the ions in the compound should add up to zero. One can also determine the charge on the cation in each compound.

Explanation of Solution

Given information:

Transition metals form cations whose charges can be determined by their chemical formula.

Transition metals cations have different charges in different compounds. Charge of a transition metal ion cannot be simply determined from its location on the periodic table. Chemical formulas can be used to determine the charge of the ion.

To determine the charge on transition metal cations, one uses the charges on known ions and apply the rule of zero charge. For example, when iron combines with oxygen, it forms two types of compounds; Fe₂O₃ and FeO. From the periodic table it is known that oxygen form ions with -2 charge. According to rule of zero charge, the total charges on the ions in the compound should add up to zero.

In Fe₂O₃, the charges on 3 oxygen anions add up to -6. So each cation must have a charge of + 3.

In FeO, the charge on a single oxygen anion is -2. So each cation must also have a charge of + 2.

In this way one can determine the charge on transition metal cations from chemical formula.

Conclusion

Transition metals are responsible for colors in paints, pigments and gem stones. They combine with nonmetals to form ionic compounds. Most transition metals have more than one ion charge.