# 7.5: Transition Metal Ions

Most of us are familiar with the common coins: penny, nickel, quarter. In some areas (such as Las Vegas), you might see large amounts of silver dollars (these get a little heavy in your pocket). But most of us have probably never seen a platinum eagle - an eagle coin, but one that is held primarily by collectors. If you were to take a one-ounce platinum eagle into a store and try to buy one hundred dollars worth of items, the store owner most likely would not believe you when you told them the coin was worth one hundred dollars. It would also be awkward and annoying if you lost one of these coins out of your pocket. Platinum is just one of several transition metals that is worth a lot of money (gold is another one).

The group 1 and 2 elements form cations through a simple process that involves the loss of one or more outer shell electrons. These electrons come from the $$s$$ orbital and are removed very readily.

### Transition Metal Ions

Most transition metals differ from the metals of Groups 1, 2, and 13 in that they are capable of forming more than one cation with different ionic charges. As an example, iron commonly forms two different ions. It can sometimes lose two electrons to form the $$\ce{Fe^{2+}}$$ ion, while at other times it loses three electrons to form the $$\ce{Fe^{3+}}$$ ion. Tin and lead, though members of the $$p$$ block rather than the $$d$$ block, also are capable of forming multiple ions.

Figure 7.5.1: Many transition metals, shown above in pink, are capable of forming multiple types of cations.

Ionic formation for transition metals is complicated by the fact that these elements have unfilled inner $$d$$ shells. Although the next higher $$s$$ orbitals are actually at a lower energy level than the $$d$$ level, these $$s$$ electrons are the ones that are removed during ionization.

The table below lists the names and formulas of some of the common transition metal ions:

 Table 7.5.1: Common Transition Metal Ions $$1+$$ $$2+$$ $$3+$$ $$4+$$ copper (I), $$\ce{Cu^+}$$ cadmium, $$\ce{Cd^{2+}}$$ chromium (III), $$\ce{Cr^{3+}}$$ lead (IV), $$\ce{Pb^{4+}}$$ gold (I), $$\ce{Au^+}$$ chromium (II), $$\ce{Cr^{2+}}$$ cobalt (III), $$\ce{Co^{3+}}$$ tin (IV), $$\ce{Sn^{4+}}$$ mercury (I), $$\ce{Hg_2^{2+}}$$ cobalt (II), $$\ce{Co^{2+}}$$ gold (III), $$\ce{Au^{3+}}$$ silver, $$\ce{Ag^+}$$ copper (II), $$\ce{Cu^{2+}}$$ iron (III), $$\ce{Fe^{3+}}$$ iron (II), $$\ce{Fe^{2+}}$$ lead (II), $$\ce{Pb^{2+}}$$ manganese (II), $$\ce{Mn^{2+}}$$ mercury (II), $$\ce{Hg^{2+}}$$ nickel (II), $$\ce{Ni^{2+}}$$ platinum (II), $$\ce{Pt^{2+}}$$ tin (II), $$\ce{Sn^{2+}}$$ zinc, $$\ce{Zn^{2+}}$$

### Uses for Transition Metals

Because there are so many metals in this group, there are a wide variety of uses. Many of the metals are used in electronics, while others (such as gold and silver) are used in monetary systems. Iron is a versatile structural material. Cobalt, nickel, platinum, and other metals are employed as catalysts in a number of chemical reactions. Zinc is a significant component of batteries.

### Summary

• Transition metals have unfilled inner $$d$$ electron shells.
• Ions form primarily through loss of $$s$$ electrons.
• Many transition metals can form more than one ion.
• Transition metals have a wide variety of applications.

### Contributors

• CK-12 Foundation by Sharon Bewick, Richard Parsons, Therese Forsythe, Shonna Robinson, and Jean Dupon.