Family: Lanthanides and Actinides

57 La lanthanum 5.0×10−7

58 Ce cerium 1.1×10−6 $8.50/kg

59 Pr praseodymium 1.7×10−7

60 Nd neodymium 8.3×10−7 $66/kg

61 Pm promethium Almost non-existant

62 Sm samarium 2.6×10−7

63 Eu europium 9.7×10−8 $1100/kg

64 Gd gadolinium 3.3×10−7

65 Tb terbium 6.0×10−8

66 Dy dysprosium 4.0×10−7

67 Ho holmium 8.9×10−8

68 Er erbium 2.5×10−7

69 Tm thulium 3.8×10−8

70 Yb ytterbium 2.5×10−7

71 Lu lutetium 3.7×10−8 http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/f-Block_Elements/The_Lanthanides

Lanthanides consist of the elements in the f-block of period six in the periodic table. While these metals can be considered

transition metals, they have properties that set them apart from the rest of the elements.

Like any other series in the periodic table, such as the Alkali metals or the Halogens, the Lanthanides share many similar

characteristics. These characteristics include the following:

•Similarity in physical properties throughout the series

•Adoption mainly of the +3 oxidation state. Usually found in crystalline compounds)

•They can also have an oxidation state of +2 or +4, though some lanthanides are most stable in the +3 oxidation state.

•A preference for more electronegative elements (such as O or F) binding

•Ionic complexes undergo rapid ligand-exchange

These elements are different from the main group elements in the fact that they have electrons in the f orbital. After

Lanthanum, the energy of the 4f sub-shell falls below that of the 5d sub-shell. This means that the electron start to fill the 4f

sub-shell before the 5d sub-shell.

Table 1: Electron Configurations of the Lanthanide Elements(in general 4f1-145d16s2) Symbol Idealized Symbol Idealized Symbol Idealized Symbol Idealized Symbol Idealized

La 5d16s2 Nd 4f35d16s2 Eu 4f65d16s2 Dy 4f95d16s2 Tm 4f125d16s2 Ce 4f15d16s2 Pm 4f45d16s2 Gd 4f75d16s2 Ho 4f105d16s2 Yb 4f135d16s2 Pr 4f25d16s2 Sm 4f55d16s2 Tb 4f85d16s2 Er 4f115d16s2 Lu 4f145d16s2

Chemical Properties and Reactions

One property of the Lanthanides that affect how they will react with other elements is called the basicity.

Another property of the Lanthanides is their magnetic characteristics.

•oxidize rapidly in moist air

•dissolve quickly in acids

•reaction with oxygen is slow at room temperature, but they can ignite around 150-200 °C

•react with halogens upon heating

•upon heating, react with S, H, C and N

Occurrence in Nature

Each known Lanthanide mineral contains all the members of the series. However, each mineral contains different

concentrations of the individual Lanthanides. The three main mineral sources are the following:

•Monazite: contains mostly the lighter Lanthanides. The commercial mining of monazite sands in the United States is centered

in Florida and the Carolinas

•Xenotime: contains mostly the heavier Lanthanides

•Euxenite: contains a fairly even distribution of the Lanthanides

In all the ores, the atoms with a even atomic number are more abundant. This allows for more nuclear stability, as explained in

the Oddo-Harkins rule.

Applications

Metals and Alloys

The pure metals of the Lanthanides have little use. However, the alloys of the metals can be very useful. For example, the alloys

of Cerium have been used for metallurgical applications due to their strong reducing abilities.

Non-nuclear

The Lanthanides can also be used for ceramic purposes. The almost glass-like covering of a ceramic dish can be created with the

lanthanides. They are also used to improve the intensity and color balance of arc lights.

Nuclear

Like the Actinides, the Lanthanides can be used for nuclear purposes. The hydrides can be used as hydrogen-moderator carriers.

The oxides can be used as diluents in nuclear fields. The metals are good for being used as structural components. The can also

be used for structural-alloy-modifying components of reactors. It is also possible for some elements, such as Tm, to be used as

portable x-ray sources. Other elements, such as Eu, can be used as radiation sources.

89 Ac actinium Almost non-existant

90 Th thorium 4.5×10−8

91 Pa protactinium Almost non-existant

92 U uranium 1.8×10−8 $60/kg

94 Pu plutonium zero $10,000/kg

98 Cf californium zero $27billion/kg

http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/f-Block_Elements/The_Actinides

The Actinide series contains elements with atomic numbers 89 to 103 and is in the f-block of the periodic table. The series is the

row below the Lanthanide series, which is located underneath the main body of the periodic table. Lanthanide and Actinide

Series are both referred to as Rare Earth Metals. These elements all have a high diversity in oxidation numbers and all are

radioactive. The most common and known element is Uranium, which is used as nuclear fuel when its converted into plutonium,

through a nuclear reaction.

History of the Actinides

The first actinides to be discovered were Uranium by Klaproth in 1789 and Thorium by Berezelius in 1829, but most of the

Actinides were man-made products of the 20th century. Actinium and Protactinium are found in small portions in nature, as

decay products of 253-Uranium and 238-Uranium. Microscopic amounts of Plutonium are made by neutron capture by Uranium,

and yet occur naturally. Monazite is the principle Thorium ore. It is a phosphate ore that contains great amounts of Lanthanides

in it. The main Uranium ore is U3O8 and is known as pitchblende, because it occurs in black, pitch-like masses. All elements past

Uranium are man-made. Actinides require special handling, because many of them are radioactive and/or unstable. The

radiation in actinides plays a large role in the chemistry and arrangement of particles in crystals.

Common Properties

•All are radioactive due to instability.

•Majority synthetically made by particle accelerators creating nuclear reactions and short lasting.

•All are unstable and reactive due to atomic number above 83 (nuclear stability).

• All have a silvery or silvery-white luster in metallic form.

• All have the ability to form stable complexes with ligands, such as chloride, sulfate, carbonate and acetate.

•Many of the actinides occur in nature as sea water or minerals.

•They have the ability to undergo nuclear reactions.

• The emission of radioactivity, toxicity, pyrophoricity, and nuclear criticality are properties that make them hazardous to

handle.

◦Emission of Radioactivity: The types of radiation the elements possess are alpha, beta, gamma, as well as when neutrons are

produced by spontaneous fissions or boron, beryllium, and fluorine react with alpha-particles.

◦Toxicity: Because of their radioactive and heavy metal characteristics, they are considered toxic elements.

◦Pyrophoricity: Many actinide metals, hydrides, carbides, alloys and other compounds may ignite at room temperature in a

finely divided state, which would result from spontaneous combustion fires and spreading of radioactive contaminates.

◦Nuclear Criticality: If fissionable materials are combined, a chain reaction could occur resulting in lethal doses of radioactivity,

but it depends on chemical form, isotopic composition, geometry, size of surroundings, etc.

•The interaction of Actinides when radioactive with different types of phosphors will produce pulses of light.

The general electron configuration is [Rn] 5f1-14

6d1 7s

2 and that of uranium is [Rn] 5f

3 6d

1 7s

2.

Nuclear Fission Reaction of Uranium

235U + 1n → 236U → fission fragments + neutrons + 3.20 x10-11

J.

235-Uranium is bombarded with neutrons and turns into 236-Uranium. The 236-Uranium then converts into smaller pieces, 2-3

neutrons are released along with energy. These extra neutrons help create a chain reaction as more neutrons come into contact

with Uranium. This uncontrolled energy eventually leads to an explosion, which is the basis of the atomic bomb. To see a lab

presentation of what this reaction looks like click on the video below.

Applications

•Plutonium and Uranium are used as nuclear fuels and in weaponry.

•Thorium (ThO2) is used as an incandescent gas mantle from the 1880s. They are now used for cooking, gas lanterns, and for

decorative gas lights.

•The 238-Plutonium isotope… ◦Powered the Apollo-12 Lunar Mission’s left behind generator. It generated under 1.5 kW of heat

converted to electricity by thermoelectric elements.

◦Was a power source for orbiting satellites and missions to take pictures of Jupiter.

◦Powers pacemakers for the heart. The nuclear energy creates a longer lifetime use of the device.

•The 241-Americium isotope is used as ionizing sources for smoke detectors.

•Uranium is used in nuclear reactors in the form of fuel in rods suspended in water under a pressure of 70 to 150 atmospheres.