Lanthanide

Related Topics:
Lanthanides

Atomic No.	Name	Symbol
57	Lanthanum	La
58	Cerium	Ce
59	Praseodymium	Pr
60	Neodymium	Nd
61	Promethium	Pm
62	Samarium	Sm
63	Europium	Eu
64	Gadolinium	Gd
65	Terbium	Tb
66	Dysprosium	Dy
67	Holmium	Ho
68	Erbium	Er
69	Thulium	Tm
70	Ytterbium	Yb
71	Lutetium	Lu

The lanthanide (or lanthanoid) series comprises the 15 elements with atomic numbers 57 through 71, from lanthanum to lutetium. 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. Also they are used to commonly deflect UV and Infrared rays. Therefore Lanthanides are commonly used in the production of sunglass lenses.

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

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Terminology

Chemistry

Mnemonics

External links

See also