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characteristics of lanthanides and actinides

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From Wikipedia

Actinide

The actinide or actinoid (IUPAC nomenclature) series encompasses the 15 chemical elements with atomic numbers from 89 to 103, actinium to lawrencium. The actinide series derives its name from the group 3 elementactinium; although actinoid (actinide) means "actinium-like" and therefore should exclude actinium, it is usually included in the series for the purpose of comparison. Only thorium and uranium occur in more than trace quantities in nature; the other actinides are synthetic elements. The actinides are usually considered to be f-block elements; they show much more variable valence than the lanthanides. All actinides are radioactive and release energy upon radioactive decay; uranium and plutonium, the most abundant actinides on Earth, are used in nuclear reactors and nuclear weapons.

Synthesis

Like lanthanides, actinides form a family of elements with similar properties. Within actinides, there are two overlapping groups: transuranium elements, which follow uranium in the periodic table—and transplutonium elements, which follow plutonium. Compared to the lanthanides, which (except for promethium) are found in nature in appreciable quantities, most actinides are rare. The most abundant, or easy to synthesize actinides are uranium and thorium, followed by plutonium, americium, actinium, protactinium and neptunium.

At present, there are two major methods of producing isotopes of transplutonium elements: irradiation of the lighter elements with neutrons or accelerated charged particles. The first method is most important for applications, as only neutron irradiation using nuclear reactors allows to produce sizeable amounts of synthetic actinides; however, it is limited to relatively light elements. The advantage of the second method is that it allows obtaining elements heavier than plutonium, as well as neutron-deficient isotopes, which are not formed during neutron irradiation.

In 1962–1966, there were attempts in the United States to produce transplutonium isotopes using a series of 6 underground nuclear explosions. Small samples of rock were extracted from the blast area immediately after the test to study the explosion products, but no isotopes with mass number greater than 257 could be detected, despite predictions that such isotopes would have relatively long half-lives of α-decay. This inobservation was attributed to spontaneous fission owing to the large speed of the products and to other decay channels, such as neutron emission and nuclear fission.

The existence of transuranium elements was suggested by Enrico Fermi based on his experiments in 1934, and the terms "actinides" (and "lanthanides"; from Greek éidos meaning "type") were proposed in 1948 by Sergey Shchukarev.

From actinium to neptunium

Uranium and thorium were the first actinides discovered. Uranium was identified in 1789 by the German chemist Martin Heinrich Klaproth in pitchblende ore. He named it after the planet Uranus, which had been discovered only eight years earlier. Klaproth was able to precipitate a yellow compound (likely sodium diuranate) by dissolving pitchblende in nitric acid and neutralizing the solution with sodium hydroxide. He then reduced the obtained yellow powder with charcoal, and extracted a black substance that he mistook for metal. Only 60 years later, the French scientist Eugène-Melchior Péligot identified it with uranium oxide. He also isolated the first sample of uranium metal by heating uranium tetrachloride with potassium. The atomic mass of uranium was then calculated as 120, but Dmitri Mendeleev in 1872 corrected it to 240 using his periodicity laws. This value was confirmed experimentally in 1882 by K. Zimmerman.

Thorium oxide was discovered by Friedrich Wöhler in the mineral, which was found in Norway (1827). From Encyclopedia

Actinides

The actinides (sometimes called actinoids) occupy the "bottom line" of the periodic table—a row of elements normally separated from the others, placed at the foot of the chart along with the lanthanides. Both of these families exhibit unusual atomic characteristics, properties that set them apart from the normal sequence on the periodic table. But there is more that distinguishes the actinides, a group of 14 elements along with the transition metal actinium. Only four of them occur in nature, while the other 10 have been produced in laboratories. These 10 are classified, along with the nine elements to the right of actinium on Period 7 of the periodic table, as transuranium (beyond uranium) elements. Few of these elements have important applications in daily life; on the other hand, some of the lower-number transuranium elements do have specialized uses. Likewise several of the naturally occurring actinides are used in areas ranging from medical imaging to powering spacecraft. Then there is uranium, "star" of the actinide series: for centuries it seemed virtually useless; then, in a matter of years, it became the most talked-about element on Earth. Why are actinides and lanthanides set apart from the periodic table? This can best be explained by reference to the transition metals and their characteristics. Actinides and lanthanides are referred to as inner transition metals, because, although they belong to this larger family, they are usually considered separately—rather like grown children who have married and started families of their own. The qualities that distinguish the transition metals from the representative or main-group elements on the periodic table are explained in depth within the Transition Metals essay. The reader is encouraged to consult that essay, as well as the one on Families of Elements, which further places the transition metals within the larger context of the periodic table. Here these specifics will be discussed only briefly. The transition metals are distinguished by their configuration of valence electrons, or the outer-shell electrons involved in chemical bonding. Together with the core electrons, which are at lower energy levels, valence electrons move in areas of probability referred to as orbitals. The pattern of orbitals is determined by the principal energy level of the atom, which indicates a distance that an electron may move away from the nucleus. Each principal energy level is divided into sublevels corresponding to the number n of the principal energy level. The actinides, which would be on Period 7 if they were included on the periodic table with the other transition metals, have seven principal energy levels. (Note that period number and principal energy level number are the same.) In the seventh principal energy level, there are seven possible sublevels. The higher the energy level, the larger the number of possible orbital patterns, and the more complex the patterns. Orbital patterns loosely define the overall shape of the electron cloud, but this does not necessarily define the paths along which the electrons move. Rather, it means that if you could take millions of photographs of the electron during a period of a few seconds, the resulting blur of images would describe more or less the shape of a specified orbital. The four basic types of orbital patterns are discussed in the Transition Metals essay, and will not be presented in any detail here. It is important only to know that, unlike the representative elements, transition metals fill the sublevel corresponding to the d orbitals. In addition, they are the only elements that have valence electrons on two different principal energy levels. The lanthanides and actinides are further set apart even from the transition metals, due to the fact that these elements also fill the highly complex f orbitals. Thus these two families are listed by themselves. In most versions of the periodic table, lanthanum (57) is followed by hafnium (72) in the transition metals section of the chart; similarly, actinium (89) is followed by rutherfordium (104). The "missing" metals—lanthanides and actinides, respectively—are shown at the bottom of the chart. The lanthanides can be defined as those metals that fill the 4f orbital. However, because lanthanum (which does not fill the 4f orbital) exhibits similar properties, it is usually included with the lanthanides. Likewise the actinides can be defined as those metals that fill the 5f orbital; but again, because actinium exhibits similar properties, it is usually included with the actinides. One of the distinguishing factors in the actinide family is its great number of radioactive isotopes. Two atoms may have the same number of protons, and thus be of the same element, yet differ in their number of neutrons—neutrally charged patterns alongside the protons at the nucleus. Such atoms are called isotopes, atoms of the same element having different masses. Isotopes are represented symbolically in one of several ways. For instance, there is this format: where S is the chemical symbol of the element, a is the atomic number (the number of protons in its nucleus), and m the mass number—the sum of protons and neutrons. For the isotope known as uranium-238, for instance, this is shown as. Because the atomic number of any element is established, however, isotopes are usually represented simply with the mass number thus: 238U. They may also be designated with a subscript notation indicating the number of neutrons, so that this information can be obtained at a glance without it being necessary to do the arithmetic. For the uranium isotope shown here, this is written as The term radioactivity describes a phenomenon whereby certain materials are subject to a form of decay brought about by the emission of high-energy particles, or radiation. Types of particles emitted in radiation include: Isotopes are either stable or unstable, with the unstable variety, known as radioisotopes, being subject to radioactive decay. In this context, "decay" does not mean "rot"; rather, a radioisotope decays by turning into another isotope. By continuing to emit particles, the isotope of one element may even turn into the isotope of another element. Eventually the radioisotope becomes a stable isotope, one that is not subject to radioactive decay. This is a process that may take seconds, minutes, hours, days, years—and sometimes millions or even billions of years. The rate of decay is gauged by the half-life of a radioisotope sample: in other words, the amount of time it takes for half the nuclei (plural of nucleus) in the sample to become stable. Actinides decay by a process that begins with what is known as K-capture, in which an electron of a radioactive atom is captured by the nucleus and taken into it. This is followed by the splitting, or fission, of the atom's nucleus. This fission produces enormous amounts of energy, as well as the release of two or more neutrons, which may in turn bring about further K-capture. This is called a chain reaction. In the discussion of the actinides that follows, atomic number and chemical symbol will follow the first mention of an element. Atomic mass figures are available on any periodic table, and these will not be mentioned in most cases. The atomic mass figures for actinide elements are very high, as fits their high atomic number, but for most of these, figures are usually for the most stable isotope, which may exist for only a matter of seconds. Though it gives its name to the group as a whole, actinium (Ac, 89) is not a particularly significant element. Discovered in 1902 by German chemist Friedrich Otto Giesel (1852-1927), it is found in uranium ores. Actinium is 150 times more radioactive than radium, a highly radioactive alkaline earth metal isolated around the same time by French-Polish physicist and chemist Marie Curie (1867-1934) and her husband Pierre (1859-1906). More significant than actinium is thorium (Th, 90), first detected in 1815 by the renowned Swedish chemist Jons Berzelius (1779-1848). Berzelius promptly named the element after the Norse god Thor, but eventually concluded tha


From Yahoo Answers

Question:ehat are the lanthanides and actinides series called plx i need help wit this really bad

Answers:Lanthanides are also known as "rare earth" elements. There is no other name for the actinides.

Question:describe the charachteristics of actinides and lanthanides.include were they are located on the periodic table and if they are metals,non-metals,metalloids,or transition metals. HW, PLEASE HELP!

Answers:they are the transition metals. they are located in period 6 and 7; 4f and 5f block. Lanthanides are shiny and silvery-white, tarnish easily when exposed to air andreact violently with most nonmetals. They are relatively soft but their hardness increases with their atomic number. Lanthanides burn in air,and have high melting and boiling points.All actinides are radioactive.

Question:Do they belong in the same family? Which family/families do they belong in?

Answers:According to the IUPAC terminology, the lanthanoid (previously lanthanide) series comprises the fifteen elements with atomic numbers 57 through 71, from lanthanum to lutetium. All lanthanoids are f-block elements, corresponding to the filling of the 4f electron shell, except for lutetium which is a d-block lanthanoid. The lanthanoid series (Ln) is named after lanthanum. 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 actinoid (previously actinide) series encompasses the 15 chemical elements that lie between actinium and lawrencium included on the periodic table, with atomic numbers 89 - The actinoid series derives its name from the first element in the series, actinium, and ultimately from the Greek (aktis), "ray," reflecting the elements' radioactivity. Atomic No. ------------------- Name ---------------- Symbol 89 -------------- Actinium----------------- Ac 90 -------------- Thorium ----------------- Th 91 -------------- Protactinium---------------- Pa 92 -------------- Uranium ---------------- U 93 -------------- Neptunium ---------------- Np 94 --------------- Plutonium ---------------- Pu 95 --------------- Americium -------------- Am 96 ------------- Curium ---------------- Cm 97 --------------- Berkelium --------------- Bk 98 --------------- Californium ---------------- Cf 99 --------------- Einsteinium ------------- Es 100 --------------- Fermium ----------------- Fm 101 -------------- Mendelevium --------------- Md 102 --------------- Nobelium ---------------- No 103 ---------------- Lawrencium---------------- Lr So they dont belong to similar family. The actinoids are typically placed below the main body of the periodic table (below the lanthanoid series), in the manner of a footnote.

Question:when how and who decided to move the lanthanide and actinide series. im doing a report on change to the table and i figure this might be a point.

Answers:No idea who, but I know why. This was because the people wanted to contract it so it wouldn't be so long. Wikipedia the "Extended Periodic Table" to see what the long one looks like. GL on your report, by the way.

From Youtube

Toddler deciphers Lanthanides and Actinides chem symbols :43 months; Lanthanides: La=lanthanum, Ce=cerium, Pr=praseodymium, Nd=neodymium, Pm=promethium, Sm=samarium, Eu=europium, Gd=gadolinium, Tb=terbium, Dy=dysprosium, Ho=holmium, Er=erbium, Tm=Thulium, Yb=ytterbium Lu=lutetium Actinides: Ac=actinium, Th=thorium, Pa=protactinium, U=uranium, Np=neptunium, Pu=plutonium, Am=americium, Cm=curium, Bk=berkelium, Cf=californium, Es=einsteinium, Fm=fermium, Md=mendelevium, No=nobelium Lr=lawrencium