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Cations
Charges and Names
First let's look at the metals, which lose electrons to become our cations.
| All of the elements in Group I-A become
cations with a positive one charge. To name these simple, predictable ions we
simply use the name of the element - lithium ion, sodium ion, potassium ion, and so on. Elements
in Group II-A lose two electrons and take on a positive two charge. These simple,
predictable ions are called beryllium ion, magnesium ion, calcium ion and so on. |
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Now we need to deal with metals that do not form simple, predictable ions. We
saw in lesson 7 that the transition metals and the metals to the right of them
generally form more than one ion. That means that when we
use these metals we need to indicate which ion we are using.
| Each different ion needs to have its own distinct name. The modern
(and somewhat simpler) way to
name these kinds of ions is to put the charge or oxidation state in parentheses using
Roman numerals after the name of the element. For example chromium(II) ion and
chromium(III) ion. This is called the Stock name. |
| Cr3+ |
chromium(III) ion |
| Cr2+ |
chromium(II) ion |
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| An older method uses an "-ic" ending for the higher charge or
oxidation state and an "-ous" ending for the lower charge or oxidation state.
For example, chromous ion and chromic ion. (I like to remember it as
there's an "i" in "higher" and an "o" in
"lower".) |
| Cr3+ |
chromic ion |
| Cr2+ |
chromous ion |
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| When the ous/ic method of naming is used, the Latin name for the element
is often used in place of the modern name. The ions of iron, for example, can be called
ferrous ion and ferric ion. |
| Fe3+ |
ferric ion |
| Fe2+ |
ferrous ion |
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| In lesson 7 you memorized the common ions for iron and copper.
Now you also need to memorize their names. Iron forms the iron(III) ion and the iron(II) ion. The old names
for these are ferric ion and ferrous ion. Copper forms copper(II) ion and copper(I) ion.
The old names for these are cupric ion and cuprous ion. |
| Cations to remember |
| Fe3+ |
ferric ion
iron(III) ion |
Cu2+ |
cupric ion
copper(II) ion |
| Fe2+ |
ferrous ion
iron(II) ion |
Cu+ |
cuprous ion
copper(I) ion |
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| A few of the transition elements form only one ion or oxidation state. For
example zinc ion, silver ion and scandium ion. Consequently these ions do not need a Roman
numeral attached to them. |
| Zn2+ |
zinc ion |
| Ag+ |
silver ion |
| Sc3+ |
scandium ion |
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| To the right of the transition metals we have metals that
act like transition metals in that they tend to form more than one type of
ion. In that regard, gallium and the other metals below and to the right of it
must be named like transition metals with a Roman numeral or the -ic/-ous
endings. |
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A reminder, when working with ions you should learn the names and charges of the copper
ions and iron ions and the names and charges of any ions that can be predicted from the
position of the element on the periodic table. Expect to look up the charges of other ions
such as the transition elements and the metals to the right of them, and then be
able to name them correctly.
Practice with Naming Cations
| The common charges for ions of several of the elements are shown here (and
listed in exercise 2 in your workbook). Take time now to name all of these ions using both
the modern (Stock) and old names where appropriate. If the old names require using the
Latin names for the elements, they are given in the exercise 2. Check your answers on the
next page or with the instructor and then continue. |
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Answers
| Element |
Charge |
New name |
Old name |
| chromium |
+2 |
chromium(II) ion |
chromous ion |
| +3 |
chromium(III) ion |
chromic ion |
| cobalt |
+2 |
cobalt(II) ion |
cobaltous ion |
| +3 |
cobalt(III) ion |
cobaltic ion |
| copper |
+1 |
copper(I) ion |
cuprous ion |
| +2 |
copper(II) ion |
cupric ion |
| iron |
+2 |
iron(II) ion |
ferrous ion |
| +3 |
iron(III) ion |
ferric ion |
| lead |
+2 |
lead(II) ion |
plumbous ion |
| +4 |
lead(IV) ion |
plumbic ion |
| mercury |
+1 |
mercury(I) ion |
mercurous ion |
| +2 |
mercury(II) ion |
mercuric ion |
| nickel |
+2 |
nickel(II) ion |
nickelous ion |
| +3 |
nickel(III) ion |
nickelic ion |
| silver |
+1 |
silver ion |
silver ion |
| tin |
+2 |
tin(II) ion |
stannous ion |
| +4 |
tin(IV) ion |
stannic ion |
| zinc |
+2 |
zinc ion |
zinc ion |
Practice with Naming Cations
To give you some practice determining the names of cations, work
on these examples (also shown in exercise 3 in your workbook). As a review, also
write the charge or charges of the ions. Then check your answers on
the next page or with the instructor.
| Metal |
Ion
Formula(s) |
Ion
Name(s) |
| Na |
|
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| Ba |
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| Fe |
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| Mg |
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| Al |
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| Cu |
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| Ag |
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Answers
| Metal |
Ion
Formula(s) |
Ion
Name(s) |
| Na |
Na+ |
sodium ion |
| Ba |
Ba2+ |
barium ion |
| Fe |
Fe2+
Fe3+ |
iron(II) ion, ferrous ion
iron(III) ion, ferric ion |
| Mg |
Mg2+ |
magnesium ion |
| Al |
Al3+ |
aluminum ion |
| Cu |
Cu+
Cu2+ |
copper(I) ion, cuprous ion
copper(II) ion, cupric ion |
| Ag |
Ag+ |
silver ion |
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Eden Francis
Clackamas Community College
©1998, 2002 Clackamas Community College, Hal Bender
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