Inner transition element

The inner transition elements 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.

The Inner Transition Elements

* Lanthanides

57 La

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

89 Ac

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

All lanthanides except lutetium are f-block elements, corresponding to the filling of the 4f electron shell. The lanthanide series is named after lanthanum. There are also alternative arrangements which do not include either lanthanum or lutetium.

Terminology

The lanthanides, together with scandium and yttrium, are also sometimes referred to by the trivial name "rare earths", although this name is deprecated 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.

Chemistry

Lanthanides are chemically similar to each other, to scandium and yttrium. Useful comparison can also be made with the actinides, where the 5f shell is partially filled. The lanthanides are typically placed below the main body of the periodic table in the manner of a footnote. The full-width version of the periodic table shows the position of the lanthanides more clearly.

The ionic radii of the lanthanides decrease through the period — the so-called lanthanide contraction. Except for cerium (III and IV) and europium (III and II), the lanthanides occur as trivalent cations in nature. 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. 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.

Most lanthanides are widely used in lasers.

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

• USGS Rare Earths Statistics and Information

See also

• Group number of lanthanides and actinides
• Rare earth element

The actinide series encompasses the 15 chemical elements that lie between actinium and lawrencium on the periodic table with atomic numbers 89 - 103. The actinide series is named after actinium. All actinides are f-block elements except lawrencium. There are also alternative arrangements which do not include either actinium or lawrencium in the actinide series.

The actinides display less similarity in their chemical properties than the lanthanide series, for instance exhibiting a wider range of oxidation states, which initially led to 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.

The actinides are typically placed below the main body of the periodic table, in the manner of a footnote. The full-width version of the periodic table shows the position of the actinides more clearly.

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.

Phase diagram of the actinide elements.

Periodic tables

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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