Ions of Transition Elements

The transition elements are a group of elements found in the d-block of the periodic table (the region between groups 2 and 3).

The periodic table.

When it comes to forming ions, the transition elements do follow the simple pattern that most of the other elements follow.

Many transition elements have naturally occurring ions that do not have full outer shells, and many transition elements have more than one naturally occurring ion.

For example, copper has two naturally occurring ions: Cu⁺ and Cu²⁺. Neither of them has a full outer shell.

There are two different naturally occurring copper ions: Cu+ and Cu2+. Note that neither of them has a full outer shell.

This means that we cannot use the rule of full outer shells to predict which transition elements ions occur naturally. In fact, there is no simple way to predict the naturally occurring ions of transition elements, we only know what they are by observation.

One thing that does make things simpler is the fact that naturally occurring transition element ions are always positively charged (e.g. Cu⁺, Cu²⁺, Mn²⁺, Fe²⁺, Fe³⁺).

For transition element ions, we include the relative charge in the name

Because most elements only have naturally occurring ions that have full outer shells, we can usually work out what the relative charge of an ion is just from its name.

For example, if we read magnesium ion, we can work out that it must have a relative of +2 because magnesium is in group 2. Therefore, we know that its formula is Mg²⁺.

Similarly, if we read chloride ion, we can work out that it must have a relative charge of -1, because chlorine is in group 7. Therefore, we know that its formula is Cl^-.

However, this doesn't work for transition elements. For example, if we read copper ion, we have no way of knowing whether it means Cu⁺ or Cu²⁺.

Therefore, whenever we write the name of a transition element ion, we have to specify its relative charge. We do this by writing the charge in roman numerals in brackets after the element name.

For example:

Cu⁺ is called a copper (I) ion

Cu²⁺ is called a copper (II) ion

Fe²⁺ is called an iron (II) ion

Fe³⁺ is called an iron (III) ion

Note that we don't need to include a plus sign (+) because all naturally occurring transition element ions are positively charged.

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