Difference between revisions of "Inner transition element" - New World Encyclopedia
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| − | The '''inner transition | + | The '''inner transition metals''' are the two series of elements that are usually shown below all the other elements in the standard view of the [[Periodic table/standard|periodic table]], but really belong to the periods 6 and 7. The two series are the '''lanthanides''' and the '''actinides'''. The '''lanthanide''' series comprises the 14 [[chemical element|element]]s following [[lanthanum]], and the '''actinide''' series similarly comprises the 14 elements following [[actinium]]. These elements were among the last to be discovered and placed in the periodic table. Many of the actinides do not occur naturally and were synthesized in nuclear reactions Chemically the elements in each series are very similar to each other, particularly the lanthanides. Probably the most significant use is that of [[Uranium]] (U) and [[Plutonium]] (Pu) in [[nuclear power]] generation. |
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== Definition == | == Definition == | ||
| − | The definition of the inner tranisition metals is somewhat imprecise. Some include [[Lanthanum]] and [[Actinium]] to give fifteen elements in each series. From the standpoint of the electronic structure | + | The definition of the inner tranisition metals is somewhat imprecise. Some include [[Lanthanum]] and [[Actinium]] to give fifteen elements in each series. From the standpoint of the electronic structure the lanthanides are characterized by the gradual filling of the 4''f'' subshell and the actinides by the filling of the 5''f'' subshell. Consequently thse elements are also called [[Periodic table/block|f-block]] elements. In these elements, however, the outermost ''d'' and ''f'' subshells lie close together in energy leading to some irregularities in electronic structure. This in turn leads to some uncertainty about where to place the elements (see the periodic table showing [[Periodic table/electron configurations|electron configurations]]). [[Lanthanum]] and [[Actinium]], have no ''f'' electrons and most clearly fit with the group 3 elements. However [[cerium]] and [[thorium]] also have no ''f'' electrons, but are considered part of these inner transition metal series. A commmon arrangement is to place these elements between groups 3 and 4<ref>Chang, Raymond, ''Chemistry'' (9th ed.), New York: McGraw Hill, 2007.</ref> as is done here in the [[Periodic table/wide|inline table]]. |
== Lanthanides == | == Lanthanides == | ||
| − | The lanthanides are named after the element [[lanthanum]] and, together with [[scandium]] and [[yttrium]], are also sometimes referred to by the | + | The lanthanides are named after the element [[lanthanum]] and, together with [[scandium]] and [[yttrium]], are also sometimes referred to by the trivial name "rare earths." This name is not recommended by [[IUPAC]], as they are neither rare in abundance (even the least abundant, [[lutetium]], is more abundant in the Earth's crust than [[gold]]), nor are they "earths" (an obsolete term for [[oxide]]s). Note that the [[IUPAC|International Union of Pure and Applied Chemistry (IUPAC)]] are currently recommending the name '''lanthanoid''' rather than lanthanide, as the suffix "-ide" generally indicates [[anion|anions]]. They are characterized by electrons in the 4''f'' subshell. |
=== Chemistry === | === Chemistry === | ||
| − | The lanthanides are chemically similar to each other and useful comparison can also be made with the actinides, [[scandium]], and [[yttrium]]. The [[ionic radius|ionic radii]] of the | + | The lanthanides are chemically similar to each other and useful comparison can also be made with the actinides, [[scandium]], and [[yttrium]]. The [[ionic radius|ionic radii]] of the lanthanide 3+ ions decrease through the period — the so-called [[lanthanide contraction]]. Except for cerium and europium the lanthanides occur naturally in ionic compounds as ions with a 3+ charge. This oxidation state is a universal preference for these elements. As a consequence, their geochemical behaviors are a regular function of ionic radius and, therefore, atomic number. This property results in variations in the abundances of lanthanides that are used to trace natural materials through physical and chemical processes. It also makes them difficult to separate. In addition, two of the lathanides have radioactive isotopes with long half-lives (147Sm and 176Lu) that are used to date minerals and rocks from Earth, the Moon and meteorites. Lanthanides are also widely used in [[lasers]]. |
| − | + | Chemically the lanthanides more resemble the [[alkali]] or [[alkaline earth]] elements than the [[transition metal]]s in that they react with water to liberate [[hydrogen]]. Although the 3+ oxidation state is the most important the 2+ state is also important, especially for [[Europium]] (Eu) and Ytterbium (Yb), and the Cerium forms a stable 4+ ion. | |
=== Mnemonics === | === Mnemonics === | ||
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=== Chemistry === | === Chemistry === | ||
| + | [[Image:Actinide phases.gif|right|thumb|400px|Phase diagram of the actinide elements.]] | ||
The actinides display less similarity in their chemical properties than the lanthanide series, for example exhibiting a wider range of oxidation states. Initially this led to some confusion as to whether actinium, thorium and uranium should be considered d-block elements. All actinides are radioactive. Only actinium, thorium and uranium occur naturally in the earth's crust. The remaining actinides were synthesized in the 20th century by techniques such as neutron bombardment. The latter half of the series possess exceedingly short [[half-life|half-lives]]. | The actinides display less similarity in their chemical properties than the lanthanide series, for example exhibiting a wider range of oxidation states. Initially this led to some confusion as to whether actinium, thorium and uranium should be considered d-block elements. All actinides are radioactive. Only actinium, thorium and uranium occur naturally in the earth's crust. The remaining actinides were synthesized in the 20th century by techniques such as neutron bombardment. The latter half of the series possess exceedingly short [[half-life|half-lives]]. | ||
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==Reference== | ==Reference== | ||
Revision as of 19:59, 28 June 2006
The inner transition metals are the two series of elements that are usually shown below all the other elements in the standard view of the periodic table, but really belong to the periods 6 and 7. The two series are the lanthanides and the actinides. The lanthanide series comprises the 14 elements following lanthanum, and the actinide series similarly comprises the 14 elements following actinium. These elements were among the last to be discovered and placed in the periodic table. Many of the actinides do not occur naturally and were synthesized in nuclear reactions Chemically the elements in each series are very similar to each other, particularly the lanthanides. Probably the most significant use is that of Uranium (U) and Plutonium (Pu) in nuclear power generation.
| Lanthanides | 58 Ce |
59 Pr |
60 Nd |
61 Pm |
62 Sm |
63 Eu |
64 Gd |
65 Tb |
66 Dy |
67 Ho |
68 Er |
69 Tm |
70 Yb |
71 Lu |
||||||||||||||||||||||||
| Actinides | 90 Th |
91 Pa |
92 U |
93 Np |
94 Pu |
95 Am |
96 Cm |
97 Bk |
98 Cf |
99 Es |
100 Fm |
101 Md |
102 No |
103 Lr |
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Definition
The definition of the inner tranisition metals is somewhat imprecise. Some include Lanthanum and Actinium to give fifteen elements in each series. From the standpoint of the electronic structure the lanthanides are characterized by the gradual filling of the 4f subshell and the actinides by the filling of the 5f subshell. Consequently thse elements are also called f-block elements. In these elements, however, the outermost d and f subshells lie close together in energy leading to some irregularities in electronic structure. This in turn leads to some uncertainty about where to place the elements (see the periodic table showing electron configurations). Lanthanum and Actinium, have no f electrons and most clearly fit with the group 3 elements. However cerium and thorium also have no f electrons, but are considered part of these inner transition metal series. A commmon arrangement is to place these elements between groups 3 and 4[1] as is done here in the inline table.
Lanthanides
The lanthanides are named after the element lanthanum and, together with scandium and yttrium, are also sometimes referred to by the trivial name "rare earths." This name is not recommended by IUPAC, as they are neither rare in abundance (even the least abundant, lutetium, is more abundant in the Earth's crust than gold), nor are they "earths" (an obsolete term for oxides). Note that the International Union of Pure and Applied Chemistry (IUPAC) are currently recommending the name lanthanoid rather than lanthanide, as the suffix "-ide" generally indicates anions. They are characterized by electrons in the 4f subshell.
Chemistry
The lanthanides are chemically similar to each other and useful comparison can also be made with the actinides, scandium, and yttrium. The ionic radii of the lanthanide 3+ ions decrease through the period — the so-called lanthanide contraction. Except for cerium and europium the lanthanides occur naturally in ionic compounds as ions with a 3+ charge. This oxidation state is a universal preference for these elements. As a consequence, their geochemical behaviors are a regular function of ionic radius and, therefore, atomic number. This property results in variations in the abundances of lanthanides that are used to trace natural materials through physical and chemical processes. It also makes them difficult to separate. In addition, two of the lathanides have radioactive isotopes with long half-lives (147Sm and 176Lu) that are used to date minerals and rocks from Earth, the Moon and meteorites. Lanthanides are also widely used in lasers.
Chemically the lanthanides more resemble the alkali or alkaline earth elements than the transition metals in that they react with water to liberate hydrogen. Although the 3+ oxidation state is the most important the 2+ state is also important, especially for Europium (Eu) and Ytterbium (Yb), and the Cerium forms a stable 4+ ion.
Mnemonics
To remember the sequence of the lanthanide elements, various mnemonic phrases have been used. This is the most common one:
Ladies Can't Put Nickels Properly into Slot-machines. Every Girl Tries Daily, However, Every Time You Look.
In this phrase, each word's initial letter corresponds to a lanthanide element, from Lanthanum to Lutetium.
External links
Actinides
The actinide series, in a similar fashion to the lanthanides is named after the element actinium. They are characterized by electrons in the 5f subshell. Note that the International Union of Pure and Applied Chemistry (IUPAC) are currently recommending the name actinoid rather than actinide, as the suffix "-ide" is generally used to indicate anions.
Chemistry
The actinides display less similarity in their chemical properties than the lanthanide series, for example exhibiting a wider range of oxidation states. Initially this led to some confusion as to whether actinium, thorium and uranium should be considered d-block elements. All actinides are radioactive. Only actinium, thorium and uranium occur naturally in the earth's crust. The remaining actinides were synthesized in the 20th century by techniques such as neutron bombardment. The latter half of the series possess exceedingly short half-lives.
Reference
- ↑ Chang, Raymond, Chemistry (9th ed.), New York: McGraw Hill, 2007.
| Standard table | Vertical table | Table with names | Names and atomic masses (large) | Names and atomic masses (small) | Names and atomic masses (text only) | Inline F-block | Elements to 218 | Electron configurations | Metals and non metals | Table by blocks | List of elements by name |
| Groups: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 |
| Periods: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 |
| Series: Alkalis - Alkaline earths - Lanthanides - Actinides - Transition metals - Poor metals - Metalloids - Nonmetals - Halogens - Noble gases |
| Blocks: s-block - p-block - d-block - f-block - g-block |
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| General subfields within the Natural sciences |
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| Astronomy | Biology | Chemistry | Earth science | Ecology | Physics |
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