researchers trying to isolate a rare earth element, atomic number 61, proposed various working names such as i
443636
Promethium (formerly Prometheum)
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Peter B has it right -- atomic absorption will do elemental analysis.\n\nAtomic emission spectroscopy is another tack, though a bit more challenging.
766063
It's element 94 on the Periodic Table of Elements (see URL, below).  It's radioactive because nuclei of Plutonium atoms give off alpha and beta particles and gamma radiation in a process of radioactive decay.  The Wikipedia article on radioactive decay explains this well (URL below).
305128
As the sidereal year is slowing down, in 1967 the definition was switched to an atomic-based clock.\n\nIt is now based on a multiple of the vibration period of an atom of caesium-133 at rest at 0 degrees centigrade in a zero magnetic field.\n\nCaesium-133 is a stable isotope of Caesium, with a total of 55 protons and 78 neutrons. Other isotopes exist but are so unstable that Caesium is generally considered a mono-isotopic element.\n\nin 1967 the Thirteenth General Conference on Weights and Measures defined the second of atomic time in the International System of Units (SI) as\n\nthe duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.\n\nThe ground state is defined at zero magnetic field. \n\nThe definition of the second was later refined at the 1997 meeting of the BIPM to include the statement\n\nThis definition refers to a caesium atom at rest at a temperature of 0 K.\n\nThis refinement limits the definition to only the central frequency of the broad spectrum of frequencies emitted by a typical atomic clock, which contains a caesium vapor containing many atoms moving rapidly in all directions at once. The resulting Doppler effect broadens the atoms' basic frequency so that it covers a broad spectrum of frequencies. Furthermore, it indicates that the ultimate atomic clock would contain a single caesium atom at rest emitting a single frequency.
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Ununoctium (IPA pronunciation: /ˌjuːnəˈnɒktiəm/ [1]) is the temporary IUPAC name for the superheavy element 118. It has the temporary IUPAC element symbol Uuo and has an atomic number of 118. It probably shares similar properties of its group, the noble gases, resembling radon in its chemical properties, and so some researchers have referred to it as eka-radon. It is probably the second radioactive gaseous element and the first standard semiconductive gas.\n\nIgnoring nuclear instability due to radioactivity, scientists expect that ununoctium is much more chemically reactive than xenon or radon. It would likely form stable oxides (UuoO3, etc.) as well as chlorides and fluorides.\n\n-------------------------------------------\n\nOct 16, 2006 — SAN FRANCISCO (Reuters) - American and Russian scientists announced on Monday that they had discovered a superheavy element, known as 118, albeit one that has only existed in three different atoms lasting a fraction of a second over months of experiments.\n\nScientists discovered the last naturally occurring element on the periodic table in 1925 but have since sought to create new heavier elements.\n\nIn the latest experiments, scientists at the Lawrence Livermore National Laboratory in California and the Joint Institute for Nuclear Research in Dubna, Russia, bombarded californium with calcium ions to create 118 — the heaviest ever created in such experiments.\n\n"I think of this like any other journey to a new place. Why do you want to go to the moon? Why do you want to go to the top of Mount Everest?" Nancy Stoyer, a member of the Livermore team, said in explaining the significance of the discovery. "Finding it is something new, it is something interesting.\n\n"Finding it experimentally helps the theorists understand what really works for their theory and gives us more things to look for."\n\nScientists said they found their first superheavy element 118 atom in 2002, then found another two atoms in 2005 in a second round of experiments in which they fired 10 to the power of 19 calcium ions at the californium.\n\nIn the end the atoms of element 118 — also known as ununoctium — lasted 0.9 milliseconds, researchers said.\n\nAn announcement in 2002 from a Bulgarian-born researcher and others at the Lawrence Berkeley National Laboratory in California that they had found element 118 was later shown to have been a fraud.\n\n"We selected a completely different nuclear reaction, performed with completely different people in a different laboratory," Ken Moody, the Livermore team leader, told reporters. "Everything we do is checked and double checked.\n\n"The data analysis is performed by both us and our Russian colleagues. We do everything that we can possibility do to both avoid the possibility of intentional fraud and of mistaken handling of the data."
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you need a periodic table... just look for the symbol NA... and the atomic number 15, also look for it on the table.. it shud be under the 2-3 letter symbol of the element.
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At the bottom of the perodic table...\n\nThey are technetium (at. no. 43), which was the first element to be synthesized, promethium (at. no. 61), astatine (at. no. 85), francium (at. no. 87), and the transuranium elements (at. no. 93 and beyond in the periodic table). Some of these elements have since been shown to exist in minute amounts in nature, usually as short-lived members of natural radioactive decay series (see radioactivity).\n\nThe synthetic elements through at. no. 100 (fermium) are created by bombarding a heavy element, such as uranium or plutonium, with neutrons or alpha particles. The synthesis of the transfermium elements (elements with at. no. 101 or greater) is accomplished by the fusion of the nuclei of two lighter elements. Elements 101 through 106 were first produced by fusing the nuclei of slightly lighter elements, such as californium, with those of light elements, such as carbon. Elements 107 through 112 were first produced by fusing the nuclei of medium-weight elements, such as bismuth or lead, with those of other medium-weight elements, such as iron, nickel, or zinc. Element 114 was first produced by fusing the nuclei of plutonium and calcium and subsequently by fusing the nuclei of lead and krypton, as was element 116. Element 115 was produced by bombarding americium with calcium, and element 113 resulted from the radioactive decay of element 115. The claim by Lawrence Berkeley National Laboratory to have created element 118 has been retracted.)\n\nThe transfermium elements are produced in very small quantities (one atom at a time), and identification is therefore very difficult because of half-lives ranging from minutes to milliseconds and the need to identify the products by methods other than known chemical separations. This has led to controversy over reported discoveries and over the naming of the elements. It has been predicted that one isotope of element 114—containing 114 protons and 184 neutrons—would be very stable because its nucleus would have a full complement of protons and neutrons. Termed an “island of stability,” its half-life might be measured in years. However, none of the three isotopes of element 114 synthesized as yet have as many as 184 neutrons, and their half-lives are still in the millisecond range.
91317
It must be Scandium (Sc, 21)
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Lutetium is a silvery white corrosion-resistant trivalent metal that is relatively stable in air and is the heaviest and hardest of the rare earth elements. Lutetium has the highest spin quantum number of the elements, at 7.\n\nThis element is very expensive to obtain in useful quantities and therefore it has very few commercial uses. However, stable lutetium can be used as catalysts in petroleum cracking in refineries and can also be used in alkylation, hydrogenation, and polymerization applications.\n\nLutetium aluminum garnet (Al5Lu3O12) has been proposed for use as a lens material in high refractive index immersion lithography.\n\nFound with almost all other rare-earth metals but never by itself, lutetium is very difficult to separate from other elements and is the least abundant of all naturally occurring elements. Consequently, it is also one of the most expensive metals, costing about six times as much per gram as gold.
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Ununquadium (symbol Uuq. Atomic number 114) is the most recently accepted element (as of 2005).\nOther elements have been discovered and named since and included on a temporary basis provisional to universal acceptance. The most recent of these is ununhexium (symbol Uuh. Atomic number 116).\nHowever, the names of all elements above atomic number 111 are systematic, and the system is still being contested. So although systematic names would logically be preferable they are accepted only provisionally at present and may change in the future.\nSo in reality the most recently named element which has a name which will definitely not change is roentgenium (symbol Rg. Atomic number 111).
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It depends on which isotope you are atlking about.  The number of the isotope gives you the total number of nucleons (protons and neutrons) that it has.  Potasium is element number 19, so it has 19 protons (it is electrically neutral so it has just as many electrons as protons).  To find the number of neutrons just subtract 19 from the total number of nucleons.\n\nPotassium-39 has 20 neutrons, 19 protons and 19 electrons\nPotassium-40 has 21 neutrons, 19 protons and 19 electrons\nPotassium-41 has 22 neutrons, 19 protons and 19 electrons
11175
The 115th element is \n\nUnunpentium   115\nUup\n\nThe essentials\n*Name: ununpentium \n*Symbol: Uup \n*Atomic number: 115 \n*Atomic weight: [ 288 ] \n*CAS Registry ID: 54085-64-2 \n*Group number: 15 \n*Group name: Pnictogen \n*Period number: 7 \n*Block: p-block
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A two-color three-photon ionization technique, using two pulsed dye lasers, was employed to explore the high-lying energy levels of U I. A number of new U I levels in the 34 290--35 120-cm/sup -1/ region was observed.^Uncertainty in the assignment of J values to some levels known from earlier studies was also reduced or removed.\n\nHUH? Is that what you want?\n\nEDIT\nAbstract. Two-colour resonance ionization spectroscopy was used for identification of 240 new levels of 238U in the energy range of 38 500 to 41 200 cm-1. A precision of +or-0.03 cm-1 (1 SD) for the energies was obtained by using laser-induced fluorescence signals of I2 for spectral calibration. The angular momentum quantum number, J, was uniquely assigned for 134 of these levels by using angular momentum selection rules. \n\nThats a little more specific\nAnd some more\n\nAbstract. Visible and infrared absorption measurements on the  ion in tetragonal zircon-type matrix  are reported and analysed in terms of the standard parametrization scheme. The observed 17 main peaks and a number of less intense lines have been assigned and fitted to most of the 32 allowed electric dipole transitions with the root mean square error equal to . The free-ion parameters obtained for the model Hamiltonian, , ,  and , as well as the corresponding crystal-field parameters, , , ,  and , agree fairly well with the initial theoretical estimations. The results are discussed in relation to the previous spectroscopic study on the scheelite-type matrix .
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British chemist, John Newlands had the idea of arranging chemical elements in order of their relative atomic masses and he arranged his elements in columns. However, Russian chemist, Dmitri Mendeleev greatly improved on Newlands' idea and convinced other chemists to use it, so Mendeleev has been credited with the invention of the periodic table. Dmitri Mendeleev came up with his first version of the periodic table in 1864, since then more than 700 versions of the table have been proposed.\n\nNo chemistry textbook, classroom, lecture theatre or research laboratory is complete without a copy of the periodic table of the elements. Since the earliest days of chemistry, attempts have been made to arrange the known elements in ways that revealed similarities between them. However, it required the genius of Mendeleev to see that arranging elements into patterns was not enough; he realised that there was a natural plan in which each element has its allotted place, and this applies not only to the known elements but to some that were still undiscovered. Today we have the so-called long form of the table. This has emerged supreme from well over 100 designs that have been proposed since the time of Mendeleev. With the advantage of hindsight we can now see why this form of the table was bound to succeed.\n\nToday there are 111 elements recognised by IUPAC, and these are usually displayed in the form of a matrix called a periodic table. The term periodic came from the regular occurrence of certain chemical properties in the list of known elements when these are arranged in order of increasing relative mass. The common form, complete with the new group numbers (1-18) were finally agreed by the International Union of Pure Applied Chemistry, IUPAC, in 1985, after years of wrangling. In truly Parkinsonian fashion, this least important of changes has probably consumed the most effort!\n\nSince Antoine Lavoisier first defined a chemical element and drew up a table of 33 of them for his book 'Traité Elémentaire de Chimie' (Treatise on the Chemical Elements) published in 1789, there have been attempts to classify them. Lavoisier himself grouped them into four categories on the basis of their chemical properties: gases, nonmetals, metals and earths. In the first category he listed substances that we now know as oxides but which at the time had defeated all attempts at separation.\n\nThis desire to identify and classify elements continued in chemistry for another 80 years until Mendeleev stumbled upon the correct classification - the periodic table. Today the periodic table is securely based on the properties of atomic number of the nucleus and the electron energy levels which surround it. Both of these concepts postdate Mendeleev by several decades. He, however perceived them indirectly through the related properties of atomic weight and chemical valency and arrived at the periodic table in 1869.\n\nBecause atomic weight, relative atomic mass, is roughly proportional to atomic number, and because valency, which manifests itself in the chemical composition, is based on the outermost electrons of an atom, Mendeleev had chosen the two properties that in his day most nearly reflected the fundamental principles on which the table today is based. Consciously or subconsciously, he arrived at the idea that a table existed with positions that were to be occupied by the elements, rather than the other way round - that the known elements determined the arrangement of the table, as others imagined.\n\nThis being so, Mendeleev then put the 65 elements he knew into his table and at the same time pointed out the many unoccupied positions in the overall scheme. He took the further and much bolder step of predicting the properties of these missing elements. Moreover, the gap in atomic weights between cerium (140) and tantalum (182) suggested to him that a whole period of the table remained to be discovered. Later in the century many of these elements,
9075
"The transuranium elements are so called because they all lie beyond uranium; that is to say, they are elements with atomic numbers higher than 92 in the periodic table."\nThat's from the web site listed below.\nSo find a periodic chart, and look at all the elements above At. No. 92.
989104
Im pretty sure that the atomic numbers go in order on the periodic table.
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No; very few isotopes have been given individual names (there are far too many of them). The only ones I can think of are deuterium (hydrogen-2) and tritium (hydrogen-3).